Pellets, injection molded products, and extruded products

Abstract

To provide pellets containing PBS that have good blocking resistance and can be supplied stably to a molding machine. [Solution] A pellet containing PBS 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±5cm². -1 The first wavenumber range, and 1732±5cm -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 ) is 2.0 or higher.

Description

[Technical Field]

[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. [Background technology]

[0002] In modern society, paper, plastics, aluminum foil, and other materials are used in a wide range of applications, including packaging materials for various foods, pharmaceuticals, general merchandise, liquids, powders, and solids, as well as agricultural and construction materials. Plastics, in particular, excel in strength, water resistance, moldability, transparency, and cost, and are widely used as bags and containers. Plastics currently used in these applications include polyethylene, polypropylene, polystyrene, polyvinyl chloride, and polyethylene terephthalate. However, molded products made from the above 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).

[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, as all of its raw materials can be derived from plant resources, and it can achieve both good physical properties and biodegradability. Numerous studies have been 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 exhibits less roll contamination, odor and smoke during processing. Patent Document 2 also 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. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-162428 [Patent Document 2] Japanese Patent Publication No. 2018-139560 [Patent Document 3] Japanese Patent Publication No. 2024-049583 [Overview of the project] [Problems that the invention aims to solve]

[0007] Incidentally, when manufacturing molded products using pellets containing PBS, a phenomenon sometimes occurred where the pellet particles fused together and aggregated (hereinafter referred to as "blocking") when heat and / or load were 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 around 114°C. Blocking then occurred in the molding machine. This sometimes hindered the stable supply of pellets. One aspect of the present invention aims to solve the above problems and provides pellets containing PBS that have good blocking resistance and can be stably supplied to a molding machine as a feed material for injection molding, extrusion molding, etc. Another aspect of the present invention aims to provide biodegradable injection molded or extruded articles that can be stably manufactured. [Means for solving the problem]

[0008] The gist of this invention is as follows: [1] A pellet comprising 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 shows values ​​between 1680 and 1780 cm⁻¹. -1 The spectrum in the wavenumber range is 1718±5cm². -1 The first wavenumber range, and 1732±5cm -1 In 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 [1], wherein the strength ratio is 3.2 or less. [3] The pellet according to [1] or [2], wherein the strength ratio is 2.2 or greater. [4] A pellet according to any one of [1] to [3], wherein the strength ratio is 2.5 or greater. [5] The pellet according to any one of [1] to [4], 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. [6] The pellet according to any one of [1] to [5], wherein the content of polybutylene succinate contained in the pellet is 80% by mass or more. [7] The pellet according to any one of [1] to [6], 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. [8] The pellet according to any one of [1] to [7], wherein the content of a cyclic dimer consisting of succinic acid and 1,4-butanediol in the pellet is 2000 ppm by mass or less. [9] The pellet according to any one of [1] to [8], wherein the intrinsic viscosity (IV) of the pellet is 1.2 dL / g or more and 2.2 dL / g or less.

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

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

[0009] According to one aspect of the present 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 present invention, biodegradable injection molded articles or extruded articles that can be stably manufactured can be obtained. [Brief explanation of the drawing]

[0010] [Figure 1] This is a Raman chart (Lorentz-fitted Raman Spectrum) showing the results obtained by fitting the Raman spectrum measured from the pellet according to Example 1. [Modes for carrying out the invention]

[0011] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. Rather, it can be implemented with various modifications within the scope of the 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. Also, 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. Also, when numerical ranges are described stepwise, any combination of the upper and lower limits of each numerical range is also disclosed. Furthermore, in this specification, descriptions such as "at least one selected from the group consisting of XX, YY, and ZZ" mean any of XX, YY, ZZ, the combination of XX and YY, the combination of XX and ZZ, the combination of YY and ZZ, or the combination of XX, YY, and ZZ.

[0012] The inventors have further studied to solve the seemingly contradictory problems of improving the blocking resistance of pellets containing PBS and preventing the occurrence of fish eyes in molded products formed using such pellets due to poor melting of the pellets. In the process, the inventors have found that the Raman spectrum measured from the PBS pellets changes depending on the manufacturing conditions of the pellets. Specifically, the peak intensity I -1 attributed to the C=O stretching of the succinic acid unit of PBS that appears in the wavenumber range of 1732 ± 5 cm 02 (hereinafter also referred to as the "second wavenumber range") of the Raman spectrum, with respect to the peak intensity I -1 attributed to the C=O stretching of the succinic acid unit of PBS that appears in the wavenumber range of 1718 ± 5 cm 01 of the Raman spectrum (hereinafter also referred to as the "first wavenumber range"), the ratio I 01 / I 02 (hereinafter also referred to as the "intensity ratio") is significantly larger for pellets manufactured through a slow cooling process than for pellets manufactured without going through the slow cooling process, and it has been found that pellets with the intensity ratio being a specific value or more exhibit excellent blocking resistance, leading to the completion of the present invention.

[0013] 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. And the Raman spectrum measured from the pellet is 1680-1780 cm⁻¹. -1 The spectrum in the wavenumber range is 1718±5cm². -1 The first wavenumber range, and 1732±5cm -1 In 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 The 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. By having a strength ratio of 2.0 or higher, the pellets according to this embodiment exhibit excellent blocking resistance. The inventors speculate that the reason such pellets exhibit excellent blocking resistance is as follows: In the course of further investigations, the inventors observed the changes in the intensity of the peaks in the first wavenumber range and the second wavenumber range in the Raman spectrum when 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 in the first wavenumber range decreased, while the intensity of the peaks in the second wavenumber range increased. From these findings, it was concluded that the peaks in the first wavenumber range are attributed to the C=O expansion and contraction in succinic acid units of crystalline PBS, and the peaks in the second wavenumber range are attributed to the amorphous state. It is presumed that this is attributable to the expansion and contraction of the C=O unit in the succinic acid unit of PBS in state. 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 02 However, pellets with a value of 2.0 or higher are thought to exhibit excellent blocking resistance due to an optimized balance between the crystalline and amorphous states of PBS within the pellet. As a result, these pellets can be stably used in injection molding and extrusion molding, contributing to the even more stable production of injection-molded and extruded products. Furthermore, by setting the intensity ratio between 2.0 and 3.2, the occurrence of fish eyes caused by insufficient melting of the pellets in injection-molded and extruded products can be better prevented. In other words, since PBS begins to decompose at around 170°C, it is preferable to mold products at a relatively low temperature when using pellets containing PBS. However, if the molding temperature is lowered, the melting of the pellets may be insufficient, and the resulting molded product may develop fish eyes due to insufficient melting of the pellets, resulting in a molded product with a problematic appearance. However, by setting the intensity ratio to 3.2 or less, the occurrence of fish eyes in molded products molded at low temperatures can be better suppressed, and a molded product with a superior appearance can be obtained.

[0014] 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 within the pellet is more optimized.

[0015] 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 Corporation) Measurement conditions • Measurement mode: Point • Laser wavelength: 532nm • Laser output: 12mW (Neutral-reducing filter opening: 200 / 255) • Diffraction grating: 1200 gr / mm • Pinhole: 50 μm • Exposure time: 10 seconds • Total number of times: 3 • Objective lens: 100x ·Measurement temperature: 25℃

[0016] 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 succinic acid units of PBS. -1 The peak of the Raman scattering intensity has a peak top in the first wavenumber range and is 1732±5 cm. -1The Raman scattering intensity peak, which has its peak top in the second wavenumber range, and its two components are fitted using the Lorentz function shown in equation (1) below. In equation (1) below, A represents the peak intensity and w represents the full width at half maximum of the peak. X0 represents the peak position, which in this disclosure is 1718 ± 5 cm. -1 , and 1732±5cm -1 This is the result.

[0017]

number

[0018] Then, in the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), the peak intensity I in the first wavenumber range 01 and the peak intensity I in the second wavenumber range 02 The intensity ratio (I 01 / I 02 Specifically, the peak of the first wavenumber range obtained by fitting (i.e., X0 = 1718 ± 5 cm) is determined. -1 The ratio (A1 / A2) of the intensity A (hereinafter also referred to as "A1") obtained by the above formula (1) relating to the second wavenumber range, and the intensity A (hereinafter also referred to as "A2") obtained by the above formula (1) relating to the peak in the second wavenumber range, is I 01 / I 02 It corresponds to this.

[0019] <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-CH2-CH2-CO- (1) -O-(CH2)4-O- (2)

[0020] Furthermore, "constituent units derived from succinic acid" refers to the constituent units corresponding to succinic acid, that is, the constituent units formed by the reaction of the two carboxyl groups present in succinic acid. Similarly, "constituent units derived from 1,4-butanediol" refers to the constituent units corresponding to 1,4-butanediol, that is, the constituent units formed by the reaction of the two hydroxyl groups present in 1,4-butanediol. Furthermore, in this specification, the constituent units of PBS may be referred to as compound units for the compounds from which each constituent unit is derived. Specifically, for example, a constituent unit derived from succinic acid may be referred to as a "succinic acid unit," a constituent unit derived from 1,4-butanediol may be referred to as a "1,4-butanediol unit," a constituent unit derived from a carboxylic acid may be referred to as a "carboxylic acid unit," and a constituent unit derived from a diol may be referred to as a "diol unit."

[0021] 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, or even a polyester that contains no constituent units other than succinic acid units and 1,4-butanediol units at all, that is, a polyester consisting only of succinic acid units and 1,4-butanediol units, where the total number of moles of succinic acid units and 1,4-butanediol units accounts for 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, Let 1 mole be defined as the smallest ester unit that makes up the compound.

[0022] 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. In other words, 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.

[0023] 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.

[0024] 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. In other words, 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, a PBS with superior heat resistance and mechanical properties can be obtained.

[0025] 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.

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

[0027] 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 PBS. By keeping the proportion of polyfunctional compound units with three or more functions in PBS within the above range, the intrinsic viscosity of PBS can be adjusted to the following preferred range while more reliably preventing the formation of gel (unmelted material) in the polyester.

[0028] <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, particularly preferably 1.4 dL / g. Also, it is preferably 2.2 dL / g or less, particularly preferably 2.0 dL / g or less. That is, as the intrinsic viscosity of the PBS, 1.2 dL / g or more and 2.2 dL / g or less is preferable, and 1.4 dL / g or more and 2.0 dL / g or less is particularly preferable. By setting the intrinsic viscosity of the PBS within the above range, the mechanical strength can be further increased when made into a molded product, and the viscosity during melting can be adjusted to an appropriate range. As a result, high-quality injection-molded products and extrusion-molded products can be manufactured more easily. Note that the intrinsic viscosity depends on the molecular weight of the PBS, and the higher the molecular weight, the higher the intrinsic viscosity can be.

[0029] 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 as the solvent, a mixed solvent of phenol / tetrachloroethane (mass ratio 1:1) is used, and at a temperature of 30 °C, the drop seconds of a PBS solution with a concentration of 0.5 g / dL and only the mixed solvent are measured, and the intrinsic viscosity can be obtained from the following formula (2). IV = ((1 + 4K H η sp ) 0.5 - 1) / (2K H C) ··· (2) However, in formula (2), η SP = η / η0 - 1, where η is the drop seconds of the sample solution, η0 is the drop seconds of the solvent, C is the sample solution concentration (g / dL), and K H is the Huggins constant. K H adopts 0.33.

[0030] <Pellets containing PBS> There are no particular restrictions on the shape and size of the pellets containing PBS, 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 columnar, prismatic, disc-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 PBS are subjected to the solvent contact step described later, from the viewpoint of the extraction efficiency of the cyclic dimer and the like by the solvent contact step, it is preferable that the mass of one pellet is 1 to 50 mg, particularly preferably 3 to 40 mg, and even more preferably 5 to 30 mg.

[0031] <Cyclic dimer of PBS in the pellets containing PBS> In the pellets containing PBS, the content of the cyclic dimer of PBS (hereinafter also simply referred to as "cyclic dimer") is preferably 4000 mass ppm or less, particularly preferably 3500 mass ppm or less, more preferably 3000 mass ppm or less, even more preferably 2000 mass ppm or less, and even more preferably 1000 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 of the pellets can be further improved. Here, the cyclic dimer of PBS is a compound by-produced by the cyclization of 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, and refers to the cyclic dimer composed of succinic acid and 1,4-butanediol. Such a cyclic dimer can be represented, for example, by the following structural formula (3).

[0032]

Chemical formula

[0033] ​​There is no particular lower limit to the cyclic dimer content in pellets containing PBS, and it can be 0 ppm by mass. However, setting the cyclic dimer content to 0 ppm by mass may lead to an increase in the labor 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 cyclic dimer content in pellets containing PBS will be described later.

[0034] The pellets containing PBS can contain other components in addition to PBS. As one of the other components, for example, a release agent can be mentioned. Examples of the release agent include those generally used in injection molding and extrusion molding. Specifically, for example, ester compounds of polyhydric alcohols and long-chain aliphatic carboxylic acids (for example, ester compounds of stearic acid or montanic acid and ethylene glycol, glycerin, pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (for example, stearic acid, montanic acid, etc.) and stearylamine, ethylenediamine, etc., silicone compounds, etc. can be mentioned. As the blending ratio of the release agent, in order to prevent blocking of the pellets due to excessive bleeding of the release agent onto the pellet surface and improve the releasability of the molded product, based on the pellets containing PBS, 0.001 to 1% by mass is preferable, and 0.005 to 0.8% by mass is particularly preferable. Also, within a range not impairing the object of the present invention, additives can also be contained as other components. Examples of the additives include reinforcing materials such as talc, kaolin, mica, clay, bentonite, sericite, basic magnesium carbonate, aluminum hydroxide, glass flakes, glass fibers, carbon fibers, asbestos fibers, rock wool, calcium carbonate, silica sand, wollastonite, barium sulfate, glass beads, titanium oxide, non-plate-shaped fillers, or antioxidants (phosphorus-based, sulfur-based, etc.), ultraviolet absorbers, heat stabilizers (hindered phenol-based, etc.), transesterification reaction inhibitors, lubricants, antistatic agents, colorants including dyes and pigments, flame retardants (halogen-based, phosphorus-based, etc.), flame retardant aids (antimony compounds represented by antimony trioxide, zirconium oxide, molybdenum oxide, etc.), antibacterial agents, etc. The pellet containing PBS can contain other components in addition to PBS. As one of the other components, for example, a release agent can be mentioned. Examples of the release agent include those generally used in injection molding and extrusion molding. Specifically, for example, ester compounds of polyhydric alcohols and long-chain aliphatic carboxylic acids (for example, ester compounds of stearic acid or montanic acid and ethylene glycol, glycerin, pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (for example, stearic acid, montanic acid, etc.) and stearylamine, ethylenediamine, etc., silicone compounds, etc. can be mentioned. As the blending ratio of the release agent, in order to prevent blocking of the pellets due to excessive bleeding of the release agent onto the pellet surface and improve the releasability of the molded product, based on the pellets containing PBS, 0.001 to 1% by mass is preferable, and 0.005 to 0.8% by mass is particularly preferable. Also, within a range not impairing the object of the present invention, additives can also be contained as other components. Examples of the additives include reinforcing materials such as talc, kaolin, mica, clay, bentonite, sericite, basic magnesium carbonate, aluminum hydroxide, glass flakes, glass fibers, carbon fibers, asbestos fibers, rock wool, calcium carbonate, silica sand, wollastonite, barium sulfate, glass beads, titanium oxide, non-plate-shaped fillers, or antioxidants (phosphorus-based, sulfur-based, etc.), ultraviolet absorbers, heat stabilizers (hindered phenol-based, etc.), transesterification reaction inhibitors, lubricants, antistatic agents, colorants including dyes and pigments, flame retardants (halogen-based, phosphorus-based, etc.), flame retardant aids (antimony compounds represented by antimony trioxide, zirconium oxide, molybdenum oxide, etc.), antibacterial agents, etc.

[0035] <Method for producing pellets containing PBS> Pellets containing PBS 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 an ester-forming derivative thereof 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 PBS low polymer. (Step 3) Following Step 2, the obtained low polymer is gradually subjected to reduced pressure and heated to carry out a melt polycondensation reaction under a polycondensation catalyst. (Step 4) Following Step 3, 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 01 / I 02 Processing is performed to control the content of the cyclic dimer and the cyclic dimer. Furthermore, a process of air separation and sieving of pellets may be performed between step 4 and step 5, and / or after step 5.

[0036] 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 percentage of all carboxyl groups of the starting material dicarboxylic acid that react with the diol component and are esterified) is carried out until it reaches 90% or more, while removing the water and excess diol components produced in the reaction from the system, thereby obtaining a PBS low polymer.

[0037] An example of step 3, in which a melt polycondensation reaction is carried out, is a multi-stage reactor consisting of, for example, a single melt polycondensation tank or multiple melt polycondensation tanks connected in series, with the first stage being a fully mixed reactor equipped with stirring blades, and the second and third stages being horizontal plug-flow reactors equipped with stirring blades, while distilling the diol produced out of the system under reduced pressure.

[0038] 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.

[0039] Furthermore, in steps 1 and 2 above, which involve forming a low polymer of 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.Specific examples of antioxidants include, for example, Irganox 1330 (manufactured by BASF) and Irganox 1010 (manufactured by BASF), and examples of basic compounds include, for example, tertiary amines such as triethylamine, tri-n-butylamine, and benzyldimethylamine, quaternary ammonium hydroxides such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, and trimethylbenzylammonium hydroxide, lithium carbonate, sodium carbonate, sodium hydroxide, potassium carbonate, and sodium acetate.

[0040] 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 is cut; and the underwater hot cutting method, in which molten PBS is extruded into water from the nozzle hole and immediately cut.

[0041] <Intensity ratio (I 01 / I 02 ) How to adjust > The pellets containing PBS related to this disclosure 01 / I 02This can be adjusted, for example, by adjusting the temperature and time added to the pellet 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").

[0042] <Slow cooling process> The slow cooling process can be performed before or during step 4. Specifically, the PBS extruded from the die into a cooling liquid adjusted to a predetermined temperature is held in the cooling liquid in its strand form for a predetermined time. After that, it is cut to form pellets. Alternatively, the PBS extruded from the die into a cooling liquid adjusted to a predetermined temperature is cut in the cooling liquid to form pellets (step 4), and the pellets are held in the cooling liquid for a predetermined time. By slowly cooling molten PBS, the orientation of the molecules in the molten PBS is promoted, making it possible to appropriately develop the crystalline structure of PBS. However, if molten PBS is extruded into, for example, a room temperature (25°C) environment, the PBS will cool rapidly, and the molecules of PBS will be fixed in a randomly oriented state. 01 / I 02 It is difficult to set it to 2.0 or higher.

[0043] Here, the temperature of the cooling liquid used to extrude the molten PBS into strands is preferably 35-70°C, particularly preferably 40-65°C, and even more preferably 45-60°C. Furthermore, the time for holding the PBS within the above temperature range is 1 01 / I 02While there are no particular restrictions as long as it can be set to 2.0 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. 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 02 It can be adjusted as needed depending on the value.

[0044] Furthermore, the type of cooling liquid is not particularly limited as long as it does not react with or dissolve PBS during the above temperature range and holding time. Examples of such cooling liquids include water.

[0045] 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 3.2. This means that the proportion of crystalline PBS in the pellet becomes too high. As a result, molded products obtained using these pellets may have many fish eyes due to incomplete melting of the pellets.

[0046] <Solvent Contact Process> It is preferable to carry out a solvent contact step as step 5 following the slow cooling step described above. This step reduces the content of cyclic dimers in the pellets and 01 / I 02 This process contributes to further adjustment of the value, and by going through this process, the content of cyclic dimers in the pellet is reduced. It can be adjusted to a smaller value within the specified range, and also, I 01 / I 02 It is possible to adjust this to a higher value, preferably within the range of 2.0 to 3.2, which is 2.0 or higher. This step involves contacting the pellet obtained through the slow cooling step 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. That is, the inventors hypothesize that the cyclic dimer in the pellet is a component that inhibits the crystallization of PBS. In the slow cooling step, by forming a macroscopic crystalline structure of PBS, I 01 / I 02 However, pellets with a ratio of 2.0 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 PBS 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 PBS molecules in the pellets progresses further, and I 01 / I 02 It is considered possible to obtain pellets with a higher value within the range of 2.0 to 3.2. Furthermore, even if only the solvent contact process is performed without the slow cooling process, 01 / I 02 It is difficult to achieve a value of 2.0 or higher. In other words, in order to develop the microcrystalline structure of PBS by removing cyclic dimers 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 PBS in the pellet.

[0047] The solvent used in this process is preferably one that does not substantially dissolve PBS even when in contact with the pellet 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.

[0048] 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 molecules of PBS, 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 molecules of PBS, it is preferably 0.1 to 10 hours, particularly preferably 0.5 to 8 hours, and even more preferably 1 to 5 hours.

[0049] Specific methods for the solvent contact process described above include, for example, the methods described in i) and ii) below. i) A method in which pellets obtained through a slow cooling process and a solvent are placed in a processing tank, and after contacting them at the predetermined temperature range and for the predetermined time, the pellets are recovered from the processing tank; ii) A method of continuously supplying pellets obtained through a slow cooling process to a processing tank, while flowing a solvent adjusted to the above-mentioned predetermined temperature range in parallel or countercurrent flow relative to the flow of pellets, allowing the pellets to be processed and the solvent to come into contact for a predetermined time, and then continuously recovering the processed pellets. The specific methods and apparatus used in this process are not particularly limited, but the method and apparatus described in Patent Document 3, which can continuously adjust the content of cyclic dimers in pellets, can be suitably used.

[0050] <Application> As described above, I 01 / I 02 However, pellets containing PBS with a pH of at least 2.0 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, 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. Also, I 01 / I 02 However, pellets containing PBS with a pH of at least 2.0 to 3.2, 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, 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.

[0051] <Molded products (injection molded products, extruded products)> Resin pellets for obtaining injection-molded or extruded articles may consist solely of pellets containing PBS. Alternatively, two types of pellets containing PBS with different molar ratios of succinic acid units and 1,4-butanediol units may be mixed to form resin pellets.

[0052] Injection molded articles 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. 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). [Examples]

[0053] 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. The measurement methods for the physical properties and evaluation items used in the following examples are as follows.

[0054] <Intrinsic viscosity (IV) dL / g> The following procedure was used with an Ubbelohde viscometer: A mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1) was used, and 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. The result was then 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 / η0-1, where η is the number of seconds the sample solution falls, η0 is the number of seconds the solvent falls, C is the concentration of the sample solution (g / dL), and K is the concentration of the sample solution (g / dL). H K is Huggins' constant. H 0.33 was adopted.

[0055] <Cyclic dimer content> 0.5 g of pellets were 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 the mixture was allowed to stand for 90 minutes for separation. Then, 2 mL of the supernatant was added. After collection and evaporation to dryness, 2 mL of acetonitrile was added and dissolved. After filtration through a 0.45 μm filter, elution was performed using a Shimadzu Prominence high-performance liquid chromatography system. The mobile phase was started with acetonitrile / water (volume ratio = 4 / 6) and the composition was continuously changed using a high-pressure gradient method up to acetonitrile / water (volume ratio = 9 / 1). 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.) was used for analysis. 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.

[0056] 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 procedure. The supernatant was then discarded, and the needle-shaped precipitates were collected. The obtained needle-shaped precipitates were purified by subjecting them to the above recrystallization procedure 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.

[0057] <Raman band intensity ratio (I 1720 / I 1730 )> We use "RAMAN touch" (product name, manufactured by Nanophoton Corporation) as our Raman spectrometer. The Raman spectrum of the pellets was measured using the following method. The measurement conditions were as follows: <Measurement conditions> • Measurement mode: Point · Laser wavelength: 532 nm · Laser output: 12 mW (opening degree of the light attenuation filter: 200 / 255) · Diffraction grating: 1200 gr / mm · Pinhole: 50 μm · Exposure time: 10 seconds · Integration number: 3 times · Objective lens: 100 times · Measurement temperature: 25 °C

[0058] Regarding the obtained Raman spectrum, the peak of the Raman scattering intensity having a peak top in the first wavenumber range of 1718 ± 5 cm -1 and the peak of the Raman scattering intensity having a peak top in the second wavenumber range of 1732 ± 5 cm -1 were fitted using the Lorentz function shown in the above formula (1). In the obtained fitted Raman spectrum (Lorentz-fitted Raman Spectrum), the peak intensity I 01 in the first wavenumber range and the peak intensity I 02 in the second wavenumber range, and the intensity ratio (I 01 / I 02 ) were determined. Specifically, the intensity A (hereinafter also referred to as "A1") in the above formula (1) related to the peak in the first wavenumber range obtained by fitting (i.e., X0 = 1718 ± 5 cm -1 ), and the intensity A (hereinafter also referred to as "A2") in the above formula (1) related to the peak in the second wavenumber range (i.e., X0 = 1732 ± 5 cm -1 ), I 01 / I 02 was calculated from the ratio (A1 / A2). In this example, the average value of three measurements was calculated. Specifically, three measurement samples were collected from the pellet to be measured, and for each measurement sample, the above Raman spectrum measurement, fitting, and calculation of I 01 / I 02 were performed. For each measurement sample, the average value of I 01 / I 02 was calculated, and I 01 / I 02 for each example and each comparative example was used.

[0059] <Heat fusion test> 20g of pellets were placed in a stainless steel (SUS) cylindrical container with an inner diameter of 20mm, and weights were placed on the surface of the pellet layer inside the 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, after which it was 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 visually observed. The evaluation criteria were as follows, with rank B or higher being considered a pass. Rank A: There was absolutely no fusion between pellets, and no blocking occurred at all, representing the best possible condition. Rank B: There were 5-10 small clumps, but they crumbled easily when lightly poked with a finger, and no blocking had occurred. Rank C: The pellets were fused together, forming clumps of 10 or more pellets, indicating that blocking had occurred.

[0060] <Measuring the number of fisheyes> Pellets containing PBS were dried in a nitrogen atmosphere at 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 / m²) caused by pellet melting defects in this film was analyzed. 2 The number of fisheyes was measured using the CCD camera attached to the device while the film was being deposited, at 1m. 2 The number of particles with a major axis of 200 μm or larger within 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 films is that the presence of fisheyes can be easily confirmed on thin films. Rank A: 100 pieces / m 2The following (particularly preferred): Rank B: 101-500 pieces / m 2 (preferable). 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℃-200℃-195℃-190℃-175℃ Screw rotation speed: 35 rpm Resin discharge pressure: 5 MPa Chill temperature: 30℃ Film thickness: 50 μm

[0061] (Example 1) [Preparation of catalyst for polycondensation] 100 parts by mass of magnesium acetate tetrahydrate were placed in a glass pear-shaped flask equipped with a stirrer, and 1500 parts by mass of anhydrous ethanol (purity 99% or higher) were added. Then, 65.3 parts by mass of ethyl acid phosphate (mixture mass ratio of monoester and diester: 45:55) was added, and the mixture was stirred at 23°C. After 15 minutes, it was confirmed that the magnesium acetate was completely dissolved, and then 122 parts by mass of tetra-n-butyl titanate was added. Stirring was continued for another 10 minutes to obtain a homogeneous mixed solution. This mixed solution was transferred to a pear-shaped flask and concentrated under reduced pressure using an evaporator in an oil bath at 60°C. After 1 hour, most of the ethanol had evaporated, yielding a translucent, viscous liquid. The oil bath temperature was further increased to 80°C, and the solution was further concentrated under reduced pressure of 5 Torr to obtain a viscous liquid. This liquid catalyst was dissolved in 1,4-butanediol to prepare a catalyst solution with a titanium atom content of 1.0% by mass.

[0062] [Manufacturing of pellets containing PBS] A slurry was prepared by continuously supplying 68.3 parts by mass of succinic acid, 66.8 parts by mass of 1,4-butanediol, and 0.257 parts by mass of malic acid to a slurry preparation tank, stirring, and mixing. The slurry was then continuously supplied to an esterification reaction tank, and the esterification reaction was carried out continuously at an internal temperature of 230°C and a pressure of 101 kPa to obtain a low polymer with an esterification rate of 92%.

[0063] 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 reduced pressure of 2.0 kPa at a temperature of 240°C for an average residence time of 2 hours. Next, the resulting reaction product was continuously supplied to the second stage polycondensation reactor, and a melt polycondensation reaction was carried out under reduced pressure of 0.4 kPa at a temperature of 240°C 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 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. Figure 1 shows 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. 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.

[0064] (Example 2) 25 parts by mass of pellets containing PBS obtained in Example 1 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a treatment tank and contacted at a temperature of 70°C for 4 hours (solvent contact step). The pellets that underwent the solvent contact step were dried under 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.

[0065] (Example 3) 25 parts by mass of pellets containing PBS obtained in Example 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 treatment tank and contacted at a temperature of 70°C for 4 hours (solvent contact step). The pellets that underwent the solvent contact step were dried in a nitrogen atmosphere at a temperature of 80°C. The pellets thus obtained are 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. In addition, a heat fusion test and the number of fish eyes were measured according to the method described above.

[0066] (Example 4) 25 parts by mass of pellets containing PBS obtained in Example 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 under 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. Ta.

[0067] (Comparative Example 1) In Example 1, after polymerization of PBS, the molten PBS was extracted in strand form from an outlet at the bottom of the polycondensation reaction vessel, rapidly cooled with water at 20°C, and the solidified strands were cut to form pellets. These pellets were dried in a nitrogen atmosphere at 80°C. The pellets thus obtained were then subjected to the method described above to determine their intrinsic viscosity and strength ratio (I 01 / I 02 The content of cyclic dimers was measured. In addition, a heat fusion test and the number of fish eyes were measured according to the method described above.

[0068] (Comparative Example 2) 25 parts by mass of pellets containing PBS obtained in Comparative Example 1 and a mixture of 40 parts by mass of ethanol and 60 parts by mass of water were continuously supplied to a treatment tank and subjected to contact treatment at a temperature of 70°C for 4 hours. The obtained pellets were dried under a nitrogen atmosphere at a temperature of 80°C. The intrinsic viscosity and strength ratio (I) of the thus obtained 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 number of fish eyes were measured according to the method described above.

[0069] (Comparative Example 3) 25 parts by mass of the pellets obtained in Comparative Example 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 under a nitrogen atmosphere at a temperature of 80°C. The obtained pellets 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.

[0070] (Comparative Example 4) In Example 1, after polymerization of PBS, the molten PBS was extruded into water at 20°C through an outlet at the bottom of the polycondensation reaction vessel. The molten PBS was immediately cut and pelletized, and the pellets were held in water at 20°C for 1 minute while applying a linear velocity to the water. The pellets were then 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. The 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.

[0071] Table 1 shows the measurement results for each pellet related to Examples 1-4 and Comparative Examples 1-4, as well as the results of the heat fusion test and the measurement of the number of fish eyes.

[0072] [Table 1]

[0073] From Table 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 exhibit 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 using such pellets allows for the production of extruded and injection-molded products with excellent appearance, where 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 molded articles 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 give molded articles with an excellent appearance can be obtained, and biodegradable injection molded or extruded molded articles that do not have appearance defects such as fish eyes can be obtained and can be stably manufactured can be obtained.

Claims

1. A pellet containing polybutylene succinate having a first constituent unit derived from succinic acid and a second constituent unit derived from 1,4-butanediol as its main constituent units, The Raman spectrum measured from the pellet shows values ​​of 1680–1780 cm⁻¹. －１ The spectrum in the wavenumber range is 1718±5 cm⁻¹. －１ The first wavenumber range, and 1732±5 cm －１ In 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 more.

5. 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.

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

7. 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.

8. 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 2000 ppm by mass or less.

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

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

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

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