Polyester composition, pellets, injection molded articles, and extruded articles

Abstract

To provide a polyester composition that is less likely to generate odor even when heated during molding. [Solution] A polyester composition comprising a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, wherein the first structural unit comprises at least structural unit A-1 derived from sebaciic acid, and the second structural unit comprises at least structural unit B derived from 1,4-butanediol, and the polyester composition The content of a cyclic ester compound having a specific structure relative to the given substance is 1 ppm by mass or more and less than 390 ppm by mass.

Description

[Technical Field]

[0001] The present invention relates to a polyester composition containing a polyester having at least sebacic acid units, pellets of the polyester composition, injection-molded and extruded articles of the pellets, a method for producing the polyester composition, and a method for reducing the odor of the polyester composition. [Background technology]

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

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

[0004] Patent Documents 1 and 2 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 in a biodegradable resin composition. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2022-157778 [Patent Document 2] Japanese Patent Publication No. 2023-55686 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] Compared to PBS and PBSA, PBSSe has superior moldability and biodegradability, including marine biodegradability. For this reason, the inventors have been diligently studying it as a next-generation biodegradable plastic. In the process, when manufacturing injection-molded or extruded articles using polymer pellets containing PBSSe, a pungent odor characteristic of the work environment was sometimes generated when the pellets were heated and plasticized (melted).

[0007] The inventors recognized that, in order to commercialize molded articles containing PBSSe, the odor generated during heating is an issue that absolutely must be resolved, from the perspective of improving the working environment at the manufacturing site.

[0008] One aspect of this disclosure aims to provide polyester compositions and pellets that do not easily generate odor even when heated. Another aspect of this disclosure aims to provide a method for producing a polyester composition and pellets that do not generate odor. Alternatively, the present invention aims to provide injection-molded articles and extruded articles that can be molded while suppressing the generation of odors. Furthermore, another aspect of the present invention aims to provide a method for producing a polyester composition that is less likely to generate odors even when heated during molding. Yet another aspect of the present invention aims to provide a method for reducing the odor of a molten polyester composition. [Means for solving the problem]

[0009] The gist of this invention is as follows: [1] A polyester composition comprising a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, The first constituent unit includes at least one constituent unit A-1 derived from sebacic acid, The second constituent unit includes at least one constituent unit B derived from 1,4-butanediol, A polyester composition wherein the content of a first cyclic ester compound represented by the following structural formula (I) in the polyester composition is 1 ppm by mass or more and less than 390 ppm by mass.

[0010] [ka]

[0011] [2] The polyester composition according to [1], wherein the content of the first cyclic ester compound is 350 ppm by mass or less. [3] The polyester composition according to [1] or [2], wherein the content of the first cyclic ester compound is 320 ppm by mass or less. [4] The polyester composition according to any one of [1] to [3], wherein the proportion of the constituent unit A-1 in the first constituent unit is 4 mol% or more and 100 mol% or less. [5] The polyester composition according to any one of [1] to [4], wherein the proportion of the constituent unit B in the second constituent unit is 10 mol% or more and 100 mol% or less. [6] The polyester composition according to any one of [1] to [5], wherein the content of the second structural unit with respect to the total number of moles of the structural units of the polyester is 49 mol% or more and 51 mol% or less. [7] The polyester composition according to any one of [1] to [6], wherein at least one selected from the group consisting of the dicarboxylic acid and the diol is derived from biomass resources. [8] The polyester composition according to any one of [1] to [7], wherein the bio-based carbon content determined by Method B of ASTM D6866-18 is 0.1% or more and 100% or less. composition. [9] The polyester composition according to any one of [1] to [8], wherein the ratio of the structural unit A-1 to the total number of moles of the structural units of the polyester is 5 mol% or more.

[10] The polyester composition according to any one of [1] to [9], wherein the first structural unit further contains a structural unit A-2 derived from a dicarboxylic acid other than sebacic acid.

[11] The polyester composition according to

[10] , wherein the structural unit A-2 contains at least one structural unit selected from the group consisting of a structural unit derived from succinic acid, a structural unit derived from terephthalic acid, and a structural unit derived from adipic acid.

[12] The polyester composition according to

[11] , wherein the structural unit A-2 contains at least a structural unit derived from succinic acid.

[13] The polyester composition according to

[12] , wherein the content of the second cyclic ester compound represented by the following structural formula (II) with respect to the polyester composition is less than 3000 mass ppm.

[0012] [Chemical formula]

[0013]

[14] The polyester composition according to

[12] or

[13] , wherein the polyester is poly(butylene succinate-sebacate).

[15] The polyester composition according to

[10] or

[11] , wherein the polyester comprises at least one polyester selected from the group consisting of poly(butylene succinate-sebacate) and poly(butylene sebacate-terephthalate).

[16] The polyester composition according to any one of [1] to [9], wherein the polyester comprises poly(butylene sebacate).

[17] Pellets comprising the polyester composition described in any of [1] to

[16] .

[18] An injection-molded polymer pellet comprising at least the pellets described in

[17] .

[19] An extruded polymer pellet comprising at least the pellets described in

[17] . A method for producing a polyester composition according to any one of [1] to

[16] , A step of obtaining a polymer composition containing the polyester by polycondensing a polymerization component containing at least one selected from the group consisting of sebaciic acid and ester derivatives of sebaciic acid, and 1,4-butanediol. A step of obtaining pellets of the polymer composition, A method for producing a polyester composition, comprising the steps of: contacting pellets of the polymer composition with a contact treatment agent containing at least a water-soluble organic solvent to remove at least a portion of the first cyclic ester compound contained in the pellets of the polymer composition to obtain the polyester composition.

[21] A method for producing the polyester composition according to

[20] , wherein the water-soluble organic solvent comprises ethanol.

[22] A polyester composition that reduces the generation of odor during melting, The polyester composition is The present invention relates to a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, wherein the polyester has a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, the first structural unit includes at least structural unit A-1 derived from sebacic acid, and the second structural unit includes at least 1, It contains constituent unit B derived from 4-butanediol, A polyester composition in which the generation of odor during melting is reduced by setting the content of the first cyclic ester compound represented by the following structural formula (I) in the polyester composition to 1 ppm by mass or more and less than 390 ppm by mass.

[0014] [ka]

[0015]

[23] A method for reducing the odor of a molten polyester composition, The polyester composition comprises a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, wherein the first structural unit comprises at least structural unit A-1 derived from sebacic acid, and the second structural unit comprises at least structural unit B derived from 1,4-butanediol. The odor reduction method described above is: A method for reducing odor, comprising the step of setting the content of a first cyclic ester compound represented by the following structural formula (I) in the polyester composition to 1 ppm by mass or more and less than 390 ppm by mass.

[0016] [ka] [Effects of the Invention]

[0017] According to one aspect of this disclosure, a polyester composition and pellets that do not easily generate odor even when heated can be obtained. Also according to one aspect of this disclosure, injection molded articles and extruded articles that can be molded without generating odor or while suppressing odor generation can be obtained. Furthermore, according to one aspect of this disclosure, a method for producing a polyester composition that does not easily generate odor even when heated during molding can be obtained. Furthermore, according to one aspect of this disclosure, a method for reducing the odor of a molten polyester composition can be obtained. [Brief explanation of the drawing]

[0018] [Figure 1] This is a schematic diagram illustrating one aspect of a part of the pellet manufacturing process (esterification reaction step) related to this disclosure. [Figure 2] This is a schematic diagram illustrating one aspect of a part of the manufacturing process (polycondensation process) of the polyester composition pellets according to the present disclosure. [Figure 3] This is a schematic diagram illustrating one aspect of a part of the pellet manufacturing process (solvent contact process / cyclic dimer separation process) related to this disclosure. [Figure 4] This is a schematic diagram illustrating one aspect of a part of the pellet manufacturing process (drying process) related to this disclosure. [Figure 5] This is an HPLC chromatogram of the polymer composition containing PBSSe according to Example 1. [Modes for carrying out the invention]

[0019] The embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments. It is not a fixed formula, but rather can be implemented with various modifications within the scope of its essence.

[0020] 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.

[0021] Furthermore, in this specification, expressions representing numerical ranges, such as "XX or greater," "YY or less," and "XX to YY," mean numerical ranges that include 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. Moreover, in this specification, for example, a statement such as "at least one selected from the group consisting of XX, YY, and ZZ" means either XX only, YY only, ZZ only, 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. In this specification, when descriptions such as "one aspect" or "one embodiment" appear multiple times, they do not necessarily refer to the same aspect, but may refer to different aspects.

[0022] Further investigation by the inventors revealed that the odor observed when a polyester composition containing PBSSe was melted was not limited to PBSSe, but was also observed in polyester compositions containing polybutylene sebacate (PBSe) and polybutylene sebacate terephthalate (PBSeT). On the other hand, no such odor was observed when polyester compositions containing polybutylene succinate (PBS) or polybutylene succinate adipate (PBSA) were heated and melted. From this, the inventors presumed that the odor was caused by sebaic acid (Se).

[0023] Based on these estimations, the inventors performed gas sampling in a sampling bag near the die that extrudes the molten resin into strands at a manufacturing site for a polyester composition containing PBSSe, which was found to emit an odor when heated and melted. The sample was then placed in a Tenax collection tube, heated at 180°C for 30 minutes, and then pre-treated at 60°C for 60 minutes to adsorb volatile (odor) components onto SPME (Solid Phase Micro Extraction) fibers, followed by so-called odor-sniffing GC / MS analysis. Specifically, gas chromatography-mass spectrometry (GC / MS) was performed on the odor components emitted when the polyester composition melted. For each separated component, a specialist in odor-sniffing GC / MS analysis simultaneously smelled the odor of the gas guided in two directions—to the GC / MS analyzer and an odor confirmation branch pipe—to link each separated component to the odor. In this analysis, the PBSSe in the composition had a content of 89 mol% of succinic acid-derived components and 11 mol% of sebacic acid-derived components relative to the total number of moles of the first component. In this specification, PBSSe in which the first component consists of 89 mol% succinic acid-derived components and 11 mol% sebacic acid-derived components may be referred to as "PBSSe(89 / 11)". Similarly, polyesters in which the first component contains components derived from two or more dicarboxylic acids may also be referred to in the same manner.

[0024] Furthermore, the results of the odor-smearing GC / MS analysis described above showed that in the GC / MS chromatogram, a clear odor was detected only from the peak corresponding to the cyclic ester compound of sebacic acid and 1,4-butanediol, shown in the following structural formula (I) (hereinafter sometimes referred to as "the first cyclic ester compound" or "BSe1"). From this, it is considered that the component that produces this peak is the odor-causing substance. In addition, this peak was not observed in the GC / MS chromatogram of PBS, which does not contain structural units derived from sebacic acid. Therefore, it is considered that BSe1 is the substance that causes odor when polymer compositions containing polyester with structural units derived from sebacic acid are melted.

[0025] [ka]

[0026] From the above considerations, it is considered that reducing the content of BSe1, represented by the above structural formula (I), in a polyester composition containing a polyester having structural units derived from sebaic acid is effective in reducing odor during heating and melting.

[0027] Therefore, the inventors prepared pellets with a reduced BSe1 content (hereinafter simply referred to as "treated pellets") by subjecting pellets of a polyester composition containing PBSSe(89 / 11), which generates an odor when heated and melted, to a process of contact with an aqueous ethanol solution (ethanol content = 50% by volume, temperature 70°C) (hereinafter simply referred to as the "solvent contact process"). Four types of treated pellets were prepared by subjecting the solvent contact process to 1 hour, 2 hours, 5 hours, and 7 hours. HPLC analysis was performed on each treated pellet to determine the BSe1 content, and the odor was evaluated when the treated pellet was heated to 230°C and melted, and the correlation between the BSe1 content and the intensity of the odor was investigated.

[0028] Regarding the evaluation of the odor, 3g of the polyester composition pellets to be evaluated were placed in an aluminum dish, covered, and the dish was placed on a hot plate heated to 230°C. After visually confirming that the pellets had completely melted and become transparent, five subjects brought their noses within approximately 3cm of the dish, and the odor intensity was determined according to the following 6-level odor intensity scale. <6-level odor intensity scale> 0 points: Odorless 1 point: A smell that can finally be detected. 2 points: A faint odor that can be identified. 3 points: Easily detectable odors 4 points: Strong odor 5 points: Strong odor

[0029] Next, the evaluation was performed using the judgment results based on the above 6-level odor intensity scale, according to the following criteria. Table 1 shows the BSe1 content of each treated pellet and the odor evaluation results.

[0030] <Odor Evaluation Criteria> -: All five subjects scored 0, or the worst score was 1. +: The worst rating is 2 points. ++: The worst possible rating is 3 points. +++: The worst possible rating is 4 points. ++++: The worst rating is 5 points.

[0031] [Table 1]

[0032] Next, for two types of treated pellets of a polyester composition containing PBSe, which generates an odor upon heating and melting, the BSe1 content was measured and the intensity of the odor during melting was evaluated in the same manner as described above. These treated pellets were subjected to a solvent contact process using an aqueous ethanol solution (ethanol content = 80 vol%) as a contact agent at a temperature of 25°C for 24 hours or at a temperature of 50°C for 7 hours. The results are shown in Table 2 below.

[0033] [Table 2]

[0034] Furthermore, two types of treated pellets were obtained by subjecting a polyester composition pellet containing PBSeT(46 / 54), which generates an odor upon heating and melting, to an aqueous ethanol solution (ethanol content = 80% by volume, temperature 70°C) as a contact agent, and performing a solvent contact process for 5 hours or 8 hours. The BSe1 content was measured and the intensity of the odor during melting was evaluated in the same manner as described above. The results are shown in Table 3 below.

[0035] [Table 3]

[0036] Based on the above experimental results, the inventors have recognized that in a polyester composition containing a polyester having at least one structural unit derived from sebacic acid as the first structural unit, having a BSe1 content of less than 390 ppm is effective in reducing odor during heating and melting.

[0037] In other words, a polyester composition according to one aspect of the present disclosure includes a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol. The first structural unit includes at least structural unit A-1 derived from sebacic acid, and the second structural unit includes at least structural unit B derived from 1,4-butanediol. Furthermore, the content of the first cyclic ester compound (BSe1) represented by the following structural formula (I) in the polyester composition is 1 ppm by mass or more and less than 390 ppm by mass.

[0038] [ka]

[0039] Furthermore, a polyester composition according to one aspect of the present disclosure includes a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, wherein the polyester has a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, the first structural unit includes at least structural unit A-1 derived from sebacic acid, and the second structural unit includes at least a structural unit derived from 1,4-butanediol The polyester composition contains unit B, and the content of the first cyclic ester compound (BSe1) represented by the above structural formula (I) in the polyester composition is set to 1 ppm by mass or more and less than 390 ppm by mass, thereby reducing the generation of odor during melting.

[0040] Furthermore, one aspect of the present disclosure is a method for reducing the odor of a molten polyester composition, wherein the polyester composition comprises polyester, the polyester comprising a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, the first structural unit comprising at least structural unit A-1 derived from sebacic acid, and the second structural unit The odor reduction method includes at least one constituent unit B derived from 1,4-butanediol. The method includes a step of setting the content of the first cyclic ester compound (BSe1) represented by the above structural formula (I) in the polyester composition to 1 ppm by mass or more and less than 390 ppm by mass.

[0041] As described above, the BSe1 content in the polyester composition according to this disclosure is less than 390 ppm by mass, more preferably 350 ppm by mass or less, and particularly preferably 320 ppm by mass or less. On the other hand, as a lower limit for the BSe1 content, from the viewpoint of reducing the generation of odor when heated at high temperatures, it is preferable that it be 0 ppm by mass. However, from the viewpoint of reducing the environmental burden when obtaining a polyester composition with a low BSe1 content, the lower limit of the BSe1 content in the polyester composition according to this disclosure is set to 1 ppm by mass or more.

[0042] In other words, one method for obtaining a polyester composition with a low BSe1 content includes the steps of: polycondensing a polymerization component containing at least one selected from the group consisting of sebaic acid and ester derivatives of sebaic acid, and 1,4-butanediol, to obtain a polymer composition containing polyester; obtaining pellets of the polymer composition; and contacting the pellets of the polymer composition with a contact treatment agent containing at least a water-soluble organic solvent to remove cyclic ester compounds such as BSe1 contained in the pellets of the polymer composition to obtain the polyester composition.

[0043] Furthermore, attempting to obtain a polyester composition with a BSe1 content of 0 ppm by mass from a polymer composition may lead to an increased environmental burden. Specifically, for example, it may require a long time to process the polymer composition pellets in the solvent contact process, or a large amount of contact agent may have to be used. Therefore, the lower limit of the BSe1 content in the polyester composition according to this embodiment is 1 ppm by mass or more, preferably 10 ppm by mass or more, and more preferably 50 ppm by mass or more. That is, the BSe1 content is preferably 1 ppm by mass or more and less than 390 ppm by mass, preferably 10 ppm by mass or more and 350 ppm by mass or less, and more preferably 50 ppm by mass or more and 320 ppm by mass or less.

[0044] In this disclosure, the polymer composition refers to a polymerized polyester obtained by polycondensation of the polymer components, which has not undergone a removal process for cyclic ester compounds containing BSe1, such as the solvent contact process described later. The polyester composition according to this disclosure is obtained by removing at least a portion of the cyclic ester compounds from the polymer composition, thereby reducing the BSe1 content to less than 390 ppm by mass.

[0045] As described above, by setting the content of BSe1 in a polyester composition containing a polyester having a structural unit derived from sebacic acid as the first structural unit to less than 390 ppm by mass, the odor of the polyester composition when it melts at high temperatures can be reduced. Such polyester compositions can be obtained, for example, by a method that includes a solvent contact step in which BSe1 is extracted and removed from polymer composition pellets using a contact treatment agent containing a water-soluble organic solvent, as described above. With this method, in polymer compositions containing polyesters having succinic acid units in addition to sebacic acid units, such as PBSSe, a cyclic ester compound of succinic acid and butanediol having the structure shown in the following structural formula (II) (hereinafter, this cyclic ester compound will also be referred to as the "second cyclic ester compound" or "BS2") can be removed along with BSe1.

[0046] [ka]

[0047] As shown in the HPLC chromatogram (see Figure 5) obtained by HPLC analysis of the polymer composition containing PBSSe according to Example 1 described later, polymer compositions containing polyester having succinic acid units, such as the polymer composition containing PBSSe(89 / 11), may contain BS2. In such polymer compositions, the BS2 content tends to increase as the proportion of succinic acid units in the first constituent unit increases. When injection molded or extruded articles are manufactured using pellets of such polymer compositions as is, oligomer components containing BS2 may bleed out onto the surface of the molded article, causing powdering on the surface. However, by using a polyester composition in which at least a portion of the BS2 contained in the polymer composition is removed, and the BS2 content is less than 3000 ppm, it is possible to obtain a molded article in which powdering on the surface is reduced / prevented. In the polyester composition according to this disclosure, from the viewpoint of suppressing oligomer bleed-out to the surface of the molded product, the BS2 content is preferably less than 3000 ppm by mass, more preferably 2500 ppm by mass or less, and particularly preferably 2000 ppm by mass or less. Furthermore, there is no particular lower limit to the BS2 content, but for the same reasons as above for setting the lower limit of the BSe1 content at 1 ppm by mass, it is preferably 1 ppm by mass or more, preferably 100 ppm by mass or more, and more preferably 500 ppm by mass or more. In other words, the BS2 content is preferably 1 ppm by mass or more and less than 3000 ppm by mass, more preferably 100 ppm by mass or more and 2500 ppm by mass or less, and particularly preferably 500 ppm by mass or more and 2000 ppm by mass or less.

[0048] <Polyester composition> The polyester compositions relating to this disclosure are described in detail below. The polyester composition comprises a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, and a predetermined amount of the BSe1.

[0049] Furthermore, in the polyester, the first constituent unit includes at least a constituent unit A-1 derived from sebacic acid, and the second constituent unit includes at least a constituent unit B derived from 1,4-butanediol. More specifically, the polyester mainly comprises a first constituent unit derived from a dicarboxylic acid and a second constituent unit derived from a diol, the first constituent unit includes at least a constituent unit A-1 derived from sebacic acid, and the second constituent unit includes at least a constituent unit B derived from 1,4-butanediol.

[0050] Specifically, for example, PBSe according to one aspect of the present disclosure has as its main constituent units a sebacic acid unit (Se)A-1 represented by the following structural formula (III), and a 1,4-butanediol unit (B) represented by the following structural formula (IV).

[0051] -OC-(CH2)8-CO- (III) -O-(CH2)4-O- (IV)

[0052] In this specification, "first structural unit derived from dicarboxylic acid" means the structural unit corresponding to the dicarboxylic acid, that is, the structural unit formed by the reaction of the two carboxyl groups of the dicarboxylic acid. Similarly, "second structural unit derived from diol" means the structural unit corresponding to the diol, that is, the structural unit formed by the reaction of the two hydroxyl groups of the diol. The same applies to "structural unit A-1 derived from sebacic acid" and "structural unit B derived from 1,4-butanediol". Furthermore, in this specification, the structural units of polyester may be referred to as compound units corresponding to the compounds from which each structural unit is derived. Specifically, for example, the first structural unit derived from dicarboxylic acid may be referred to as the "dicarboxylic acid unit", the second structural unit derived from diol as the "diol unit", the structural unit derived from sebacic acid as the "sebacic acid unit", and the structural unit derived from 1,4-butanediol as the "1,4-butanediol unit".

[0053] Furthermore, "main constituent unit" usually means that the constituent unit accounts for 80 mol% or more of the total number of moles of polyester constituent units. Specifically, in the polyester according to this disclosure, it means that the sum of the total number of moles of the first constituent unit and the total number of moles of the second constituent unit is 80 mol% or more of the total number of moles of polyester constituent units. In addition, in the polyester according to this disclosure, the sum of the total number of moles of the first constituent unit and the total number of moles of the second constituent unit may be 90 mol% or more of the total number of moles of polyester constituent units, and may even be 100 mol%, i.e., composed of the first constituent unit and the second constituent unit. In this specification, when counting the number of moles of polyester constituent units, the smallest ester unit constituting the polyester is defined as 1 mole.

[0054] The ratio of the total number of moles of the second constituent unit to the total number of moles of the polyester constituent unit is not particularly limited, but can be between 49 mol% and 51 mol%. Similarly, the ratio of the total number of moles of the first constituent unit to the total number of moles of the polyester constituent unit according to this disclosure is not particularly limited, but can be between 49 mol% and 51 mol%, or between 49.5 mol% and 50.5 mol%. By setting the ratios of the first and second constituent units in the polyester within the above ranges, a polyester composition with excellent mechanical properties and biodegradability can be obtained.

[0055] Sebacic acid unit A-1, an essential component of polyester, is a constituent unit derived from sebacic acid, which produces BSe1, the cause of odor, and is therefore a prerequisite for the problem described in this disclosure, namely, the generation of odor.

[0056] In polyester, the ratio of sebacic acid unit A-1 to the total number of moles of the first constituent units is preferably 4 mol% or more, more preferably 10 mol% or more, particularly preferably 85 mol% or more, and even more preferably 90 mol% or more. There is no particular upper limit, but it may be 100 mol%. In other words, all of the first constituent units can be sebacic acid unit A-1. That is, based on the total number of moles of the first constituent units, the ratio of moles of sebacic acid unit A-1 is preferably 4 mol% or more and 100 mol% or less, more preferably 10 mol% or more and 100 mol% or less, and particularly preferably 80 mol% or more and 100 mol% or less. More preferably 85 mol% to 100 mol%, and particularly preferably 90 mol% to 100 mol%. In a polyester having sebacic acid unit A-1, if the ratio of moles of sebacic acid unit A-1 to the total number of moles of the first constituent units is within the above range, then the biodegradability and mechanical properties can be made even better.

[0057] Furthermore, the ratio of sebaciate unit A-1 to the total number of moles of polyester constituent units is 5. When attempting to obtain a polyester with a concentration of % or more, the resulting polymer composition tends to contain a large amount of BSe1. The inventors measured the BSe1 and BS2 content in the polymerized polyester compositions of PBSSe(89 / 11), PBSSe(80 / 20), PBSSe(74 / 26), and PBSe, and obtained the experimental results shown in Table 4 below.

[0058] [Table 4]

[0059] As shown in Table 4, we found that as the ratio of sebaciate unit A-1 to the total number of moles of constituent units of the polyester in a polyester composition containing a polyester having sebaciate unit A-1 increases, the content of BSe1 in the polyester composition also increases. Therefore, in polyester compositions containing polyester in which the proportion of sebaciate unit A-1 in the total number of moles of polyester constituent units is 5 mol% or more, it is particularly important to keep the BSe1 content below 390 ppm in order to reduce odor during heating.

[0060] When the first constituent unit has a constituent unit A-2 derived from a dicarboxylic acid other than sebaciic acid (hereinafter also referred to as "other dicarboxylic acid") in addition to the sebaciic acid unit A-1, examples of other dicarboxylic acids are not particularly limited, but include aliphatic dicarboxylic acids such as adipic acid, oxalic acid, malonic acid, succinic acid, succinic anhydride, glutaric acid, pimelic acid, suberic acid, azelaic acid, undecadycarboxylic acid, dodecadycarboxylic 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. One or more of the other carboxylic acids can be used. In particular, polyesters in which the other dicarboxylic acid unit A-2 is derived from at least one dicarboxylic acid selected from the group consisting of succinic acid (S), terephthalic acid (T), and adipic acid (A) are preferred, as they can exhibit particularly excellent biodegradability and strength, along with PBSe.

[0061] The ratio of 1,4-butanediol units B to the total number of moles of the second constituent units is preferably 10 mol% or more, more preferably 80 mol% or more, particularly preferably 85 mol% or more, and even more preferably 90 mol% or more. There is no particular upper limit, but it may be 100 mol%. In other words, the second constituent unit can consist only of 1,4-butanediol units B. That is, the ratio of 1,4-butanediol units B to the total number of moles of the second constituent unit is preferably 10 mol% or more and 100 mol% or less, more preferably 80 to 100 mol%, particularly preferably 85 to 100 mol%, and even more preferably 90 to 100 mol%. Since the ratio of 1,4-butanediol units B in the second constituent unit is within the above range, a polyester with superior heat resistance and mechanical properties can be obtained.

[0062] When the second constituent unit has a constituent unit derived from a diol other than 1,4-butanediol unit B, examples of other diols 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.

[0063] Polyester may have other constituent units (hereinafter also referred to as "other constituent units") in addition to the first and second constituent units. Examples of copolymer components that may constitute other constituent units include, for example, at least one component selected from the group consisting of oxycarboxylic acids (e.g., lactic acid, glycolic acid, hydroxybutyric acid, hydroxycaproic acid, 2-hydroxy-3,3-dimethylbutyric acid, 2-hydroxy-3-methylbutyric acid, 2-hydroxyisocaproic acid, malic acid, maleic acid, citric acid, fumaric acid, etc.), esters or lactones of the oxycarboxylic acids, polymers of the oxycarboxylic acids, etc., trifunctional or more polyhydric alcohols (e.g., glycerin, trimethylolpropane, pentaerythritol, etc.), and trifunctional or more polyhydric acids or their anhydrides (e.g., propanetricarboxylic acid, pyromellitic acid, trimellitic acid benzophenonetetracarboxylic acid and their anhydrides, etc.).

[0064] 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 polyester, the intrinsic viscosity of the polyester, 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.

[0065] The content of the three or more polyfunctional compound units is preferably 0.001 to 5 mol%, and more preferably 0.05 to 0.5 mol%, based on the total number of moles of the first constituent units. By keeping the proportion of three or more polyfunctional compound units in the polyester within the above range, the formation of gel (unmelted material) in the polyester can be more reliably prevented, while the intrinsic viscosity of the polyester can be adjusted to the following preferred range.

[0066] The intrinsic viscosity (IV) of polyester is preferably 1.2 dL / g or higher, and particularly preferably 1.4 dL / g or higher. 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 polyester is preferably between 1.2 dL / g and 2.2 dL / g, and particularly preferably between 1.4 dL / g and 2.0 dL / g. By keeping the intrinsic viscosity of polyester 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 and extruded products can be manufactured more easily. Note that the intrinsic viscosity depends on the molecular weight of the polyester; the higher the molecular weight, the higher the intrinsic viscosity can be.

[0067] 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 mixed solvent of phenol / tetrachloroethane (mass ratio 1:1) as the solvent, the number of seconds for dropping a 0.5 g / dL polyester solution and the mixed solvent alone at a temperature of 30°C can be measured, and the intrinsic viscosity can be calculated from the following formula (1).

[0068] IV = ((1 + 4K H η sp ) 0.5 -1) / (2K H C)··· (1) However, in formula (1), 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 We will use 0.33.

[0069] In the polyester according to this disclosure, from the viewpoint of reducing environmental impact, it is preferable that at least one selected from the group consisting of a dicarboxylic acid that gives the first constituent unit and a diol that gives the second constituent unit is derived from biomass resources, that is, at least one selected from the group consisting of the first constituent unit and the second constituent unit is a dicarboxylic acid unit or a diol unit derived from biomass resources. Specifically, the polyester according to this disclosure preferably has a bio-based carbon content of 0.1% or more, more preferably 1% or more, and more preferably 10%, as determined by Method B of ASTM D6866-18. It is particularly preferable that the above is true. There is no particular upper limit, and it can be 100%. That is, the bio-based carbon content is preferably 0.1% or more and 100% or less, more preferably 1% or more and 100% or less, and particularly preferably 10% or more and 100% or less. There are no particular restrictions on the biomass, and it may be of plant or animal origin, for example, corn, sugarcane, wood, vegetable oil, etc.

[0070] Particularly preferred examples of polyesters relating to this disclosure include, for example, polybutylene sebacate (PBSe), polybutylene succinate sebacate (PBSSe), polybutylene sebacate terephthalate (PBSeT), polybutylene succinate sebacate terephthalate (PBSSeT), and polybutylene adipate sebacate terephthalate (PBASeT). Among these polyesters, PBSe, PBSse, and PBSeT will be described in detail.

[0071] <pbse> PBSe is a polyester whose main constituent units are 1,4-butanediol units (B) and sebacic acid units (Se)A-1. In other words, PBSe is a polyester in which the total number of moles of 1,4-butanediol units (B) and sebacic acid units (Se)A-1 is between 80 mol% and 100 mol%, and more specifically between 90 mol% and 100 mol%, relative to the total number of moles of the constituent units of PBSe.

[0072] <pbsse> PBSSe is a polyester whose main constituent units are 1,4-butanediol units (B), succinic acid units (S), and sebacic acid units (Se)A-1. In other words, PBSSe is a polyester in which the total number of moles of 1,4-butanediol units (B), succinic acid units (S), and sebacic acid units (Se)A-1 is between 80 mol% and 100 mol%, and more specifically between 90 mol% and 100 mol%, relative to the total number of moles of the constituent units of PBSSe. The ratio of succinic acid units (S) to sebacic acid units (Se) A-1 in PBSSe is preferably such that the ratio of succinic acid units is 70 mol% or more, particularly preferably 80 mol% or more, and may be 95 mol% or less, and preferably 90 mol% or less, based on the total number of moles of succinic acid units (S) and sebacic acid units (Se). Furthermore, it is even more preferable that the amount is 89 mol% or less. That is, 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, it is possible to obtain PBSSe that is superior in biodegradability, mechanical properties, and moldability.

[0073] <pbset> PBSeT is a polyester whose main constituent units are 1,4-butanediol units (B), sebacic acid units (Se)A-1, and terephthalic acid units (T). In other words, PBSeT is a polyester in which the total number of moles of 1,4-butanediol units (B), sebacic acid units (Se)A-1, and terephthalic acid units (T) is between 80 mol% and 100 mol%, and more specifically between 90 mol% and 100 mol%, relative to the total number of moles of the constituent units of PBSeT. The ratio of sebacic acid units (Se)A-1 to terephthalic acid units (T) in PBSeT is preferably such that the ratio of terephthalic acid units is 45 mol% or more, particularly preferably 50 mol% or more, and may be 95 mol% or less, preferably 80 mol% or less, and even more preferably 70 mol% or less, based on the total number of moles of sebacic acid units (Se) and terephthalic acid units (T). That is, the molar ratio of sebacic acid units to terephthalic acid in PBSeT is preferably sebacic acid units / terephthalic acid units = 55 / 45 to 20 / 80, and particularly preferably 50 / 50 to 30 / 70. By having the molar ratio of sebacic acid units to terephthalic acid units within the above range, PBSeT with superior mechanical properties and moldability can be obtained.

[0074] <Pellets containing polyester composition> There are no particular restrictions on the shape or size of the pellets containing the polyester composition, but it is preferable that they be of a shape and size suitable for use in known plastic processing methods such as injection molding and extrusion molding. Specifically, examples of shapes include cylindrical, elliptical, prismatic, disc-shaped, and spherical. In terms of size, the pellets can be of a size commonly used. Specifically, examples include those with a diameter or side length of approximately 0.7 to 12 mm. Furthermore, when producing pellets containing the polyester composition according to this disclosure by subjecting the polymer composition pellets to a solvent contact step described later, it is preferable, particularly preferable, that the mass of one pellet particle be 1 to 50 mg, more preferably 3 to 40 mg, and even more preferably 5 to 30 mg, from the viewpoint of extraction efficiency of cyclic oligomers (BSe1, BS2) by the solvent contact step.

[0075] Pellets containing the polyester composition according to this disclosure can be used as polymer pellets for molding as is. Alternatively, pellets containing the polyester composition according to this disclosure can be mixed with pellets containing other polymers different from the polyester according to this disclosure (hereinafter also referred to as "other polymer pellets") to form polymer pellets for molding. Furthermore, pellets containing the polyester composition according to this disclosure, or a mixture of such pellets and other polymer pellets, can be made into molding materials by adding other components. One example of such other components 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 (e.g., ester compounds of stearic acid or montanic acid with ethylene glycol, glycerin, or pentaerythritol), amide compounds of long-chain aliphatic carboxylic acids (e.g., stearic acid or montanic acid) with stearylamine or ethylenediamine, and silicone compounds. Regarding the proportion of the release agent, in order to prevent the pellets from blocking due to excessive bleeding of the release agent onto the pellet surface while improving the release properties of the molded product, a ratio of 0.001 to 1% by mass, and a ratio of 0.005 to 0.8% by mass, based on the pellets, is preferred.

[0076] Furthermore, additives may be included as other components, to the extent that 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, as well as 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.

[0077] <Method for producing polyester composition> The polyester composition relating to this disclosure can be manufactured, for example, through the following steps 1 to 5. (Step 1) A dicarboxylic acid component containing 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 ratio under stirring to obtain a raw material slurry. (Step 2) Following Step 1 above, the raw material slurry is heated under normal pressure or under pressure to undergo an esterification reaction to obtain a low-polymer polyester. (Step 3) Following Step 2 above, the obtained polyester low polymer is gradually subjected to reduced pressure and heated to undergo a melt polycondensation reaction under a polycondensation catalyst. (Step 4) Following Step 3 above, the molten polyester is extruded into strands and cut into pellets to obtain pellets of a polymer composition containing polyester. (Step 5) The polymer composition in the pellet obtained in Step 4 is subjected to a process to remove cyclic oligomers containing at least BSe1. Furthermore, a process of wind separation and sieving of the pellets may be performed between step 4 and step 5, and / or after step 5.

[0078] An example of the above step 2 for obtaining a polyester 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 typically 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 starting material dicarboxylic acid component that react with the diol component and are esterified, and is expressed by the following calculation formula (2). Esterification rate (%) = (Saponification value - Acid value) / Saponification value × 100 (2)

[0079] 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. However, 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 and dicarboxylic acid components can be more reliably prevented. From the viewpoint of stabilizing the esterification rate, it is preferable to keep the reaction temperature as constant as possible, for example, within ±5°C of the set temperature, and more preferably within ±2°C of the set temperature.

[0080] 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 higher, particularly preferably 70 kPa or higher, even more preferably 130 kPa or lower, and particularly preferably 110 kPa or lower. That is, 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, it is possible to more reliably prevent a decrease in the polycondensation reaction rate due to a large amount of distillation of the diol component out of the reaction system. In addition, it is possible to more reliably prevent a decrease in the polycondensation reaction rate due to dehydration decomposition of the diol component. Furthermore, 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 process, it is preferable that the esterification rate of the esterified product be 85% or higher. In this disclosure, polycondensation reaction refers to a high molecular weight polyester reaction carried out at a reaction pressure of 50 kPa or less, particularly 10 kPa or less, and esterification reaction refers to a reaction carried out at 50 to 200 kPa. The esterification rate of the esterified product is preferably 85% or higher, more preferably 88% or higher, and more preferably 90% or higher. The upper limit is better if it is higher for the subsequent polycondensation reaction, but it is usually 99%. That is, the esterification rate is preferably 85-99%, more preferably 88-99%, and particularly preferably 90-99%. By keeping the esterification rate within the above range, the polycondensation reactivity in the next polycondensation step can be improved, and scattering during the polycondensation reaction can be suppressed, and the deterioration of haze (generation of foreign matter) can be more reliably prevented.

[0081] 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.

[0082] The 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 polyester 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 polycondensation catalyst.

[0083] Furthermore, to promote the crystallization of the polyester, 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 resulting polyester having sebaciate units, 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 to the polyester in an amount of 100 to 10,000 ppm by mass, more preferably 200 to 5,000 ppm by mass, and particularly preferably 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 the polyester having sebaciate units can be obtained more reliably, and it is also advantageous in terms of cost.

[0084] Furthermore, in steps 1 and 2 above, which involve forming a low-polymer polyester, and step 3 above, which involves melt polycondensation, the aforementioned antioxidants are used to suppress side reactions such as thermal decomposition and dimerization of diols. Basic compounds can also be added. Specifically, examples of antioxidants include "Irganox 1330" (trade name, manufactured by BASF) and "Irganox 1010" (trade name, manufactured by BASF), while 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.

[0085] Examples of the above step 4 of cutting and pelletizing the polymer composition containing polyester include the strand cut method of extruding the polymer composition in a molten state through the nozzle holes of a die head using a gear pump or an extruder, cooling with water or the like while cooling and solidifying the strand and cutting the strand with a cutter, and the underwater hot cut method of extruding into water from the nozzle holes and cutting immediately in a molten state.

[0086] <Method for adjusting the content of BSe1 and BS2> The content of BSe1 and BS2 in the polymer composition can be adjusted, for example, by subjecting the pellets obtained in the above step 4 to a step (hereinafter also referred to as the "solvent contact step") of contacting with a contact treatment liquid containing at least a water-soluble organic solvent adjusted to a predetermined temperature for a predetermined time.

[0087] <Solvent contact step> The solvent contact step is a step of reducing the content of cyclic oligomers in the polymer composition in pellet form. This step has, for example, a step of contacting the pellets obtained in the above step 4 with a contact treatment liquid containing at least a water-soluble solvent capable of dissolving the cyclic oligomers adjusted to a predetermined temperature for a predetermined time. By passing through this step, at least a part of the cyclic oligomers in the pellets can be removed, and a polyester composition in which the content of BSe1 is adjusted to less than 390 mass ppm and the content of BS2 is adjusted to less than 3000 mass ppm can be obtained. And according to such a polyester composition, generation of odor from the molding material at the site of injection molding or extrusion molding can be prevented, and a significant improvement in the working environment can be achieved. Also, bleeding out of cyclic oligomers to the surface of the molded body can be suppressed, and powder spraying on the surface of the molded body can be prevented.

[0088] The contact agent used in this process is preferably one that does not substantially dissolve the polyester even when in contact with the pellets at a predetermined temperature and time, while on the other hand, can dissolve the cyclic oligomer well. Examples of such water-soluble organic solvents include C1 to C4 alcohols (methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, etc.). Among these, ethanol is particularly preferred from the viewpoint of BSe1 and BS2 removal performance. 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 oligomer, it is preferably 10% by volume or more and less than 100% by volume, more preferably 30% by volume or more and less than 100% by volume, particularly preferably 50% by volume or more and less than 100% by volume, and even more preferably 80% by volume or more and less than 100% by volume, based on the aqueous alcohol solution. When an aqueous alcohol solution is used as the contact agent, the higher the alcohol concentration, the lower the content of BSe1 and BS2 can be.

[0089] Furthermore, the temperature of the contact agent in the solvent contact process is preferably below the softening point of polyester, from the viewpoint of suppressing deformation of the pellets, for example, 70°C. The following temperatures are preferred, more preferably 65°C or lower, and particularly preferred 60°C or lower. As a lower limit, from the viewpoint of better extraction of cyclic oligomers, 30°C or higher is preferred, 35°C or higher is more preferred, and 40°C or higher is particularly preferred. That is, the temperature range of the contact agent in the solvent contact step is preferably 30 to 70°C, more preferably 35 to 65°C, and particularly preferred 40 to 60°C. As for the treatment time, from the viewpoint of better removal of BSe1, or BSe1 and BS2, 0.1 to 10 hours is preferred, more preferably 0.5 to 8 hours, and particularly preferred 1 to 5 hours. As is clear from Table 2 above, the higher the temperature in the solvent contact step, the faster the content of BSe1 and BS2 can be reduced. Therefore, in the solvent contact step, for example, by using an 80 vol% aqueous solution of ethanol as the contact agent and treating at a temperature of 70°C, the content of BSe1 and BS2 can be reduced in a shorter time. Furthermore, as is clear from Table 3 above, when using the same contact treatment solution, the longer the treatment time, the lower the content of BSe1 and BS2 can be.

[0090] Furthermore, the mass ratio (solvent / pellet) of polymer composition pellets to contact agent in the solvent contact process is preferably 1.0 or higher, more preferably 1.5 or higher, and even more preferably 2.0 or higher. In addition, the mass ratio is preferably 50.0 or lower, more preferably 30.0 or lower, and particularly preferably 20.0 or lower. That is, 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. By keeping the mass ratio within the above range, it is possible to prevent the concentration of cyclic oligomers in the contact agent from becoming too high, and to remove cyclic oligomers from the pellets more stably. Furthermore, it is possible to prevent an excessive amount of contact agent relative to the pellets, thus preventing cost increases associated with larger processing equipment and contributing to a reduction in environmental impact.

[0091] 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 the polymer composition pellets and a contact treatment agent are placed in a treatment tank, and after contacting them at the predetermined temperature range and for the predetermined time, the treated polyester composition pellets are recovered from the treatment tank (hereinafter also referred to as the "batch method" or "processing method"); ii) A method (hereinafter also referred to as the "continuous method") in which pellets of a polymer composition are continuously supplied to a treatment tank, and a contact treatment agent adjusted to the above-mentioned predetermined temperature range is flowed in a parallel or countercurrent flow relative to the flow of the pellets, and after the pellets and the contact treatment agent are in contact for a predetermined time, the treated polyester composition pellets are continuously recovered. The specific methods and apparatus used for the above-mentioned palindromic and continuous processing are not particularly limited, but as a method and apparatus related to the continuous process that can continuously adjust the content of cyclic oligomers in pellets, for example, the method and apparatus described in Patent Document 2 can be suitably used.

[0092] In the solvent contact process, it is preferable to use a fresh contact agent from the viewpoint of reducing the content of cyclic oligomers in the polymer composition pellets. However, from the viewpoint of reducing environmental impact and effectively utilizing resources, it is preferable to reuse the contact agent used in the solvent contact process. In this case, since the contact agent that has come into contact with the pellets in the solvent contact process contains cyclic oligomers, it is preferable to separate the cyclic oligomers according to their concentration and control the concentration of cyclic oligomers in the reused contact agent to be low. In particular, when the solvent contact process is a continuous process and the contact agent that has been treated in contact with the polymer composition pellets is circulated and reused, it is preferable to control the concentration of cyclic oligomers in the entire contact agent used in the solvent contact process to be low. Specifically, the contact agent that has come to contain cyclic oligomers by coming into contact with the polymer composition pellets is reused. It is preferable to separate and remove the cyclic oligomer from the contact agent in a separation step before use.

[0093] The method / apparatus (separation apparatus) for separating cyclic oligomers from a contact agent containing cyclic oligomers is not particularly limited and includes, for example, a distillation column, a crystallizer, a thin-film evaporator, a centrifuge, etc.

[0094] For example, when recycling a contact agent used in a solvent contact process, it is conceivable to separate at least a portion of the cyclic oligomer contained in the contact agent using the separation device described above, adjust (reduce) the concentration of the cyclic oligomer in the contact agent, and then use it again in the solvent contact process. Furthermore, when the solvent contact process is carried out continuously, as shown in Figure 3 described later, the contact agent that has come into contact with the pellets in the contact treatment tank (III) in Figure 3 is recovered via the contact agent recovery line (106), and the proportion of the recovered contact agent that is supplied to the separator (XI) by the contact agent supply line (111) is defined as the separation rate. From the viewpoint of achieving a higher level of compatibility between the recyclability of the contact agent and the quality of the pellets (low content of cyclic dimers), it is preferable that the separation rate be 20% by mass or more. In particular, it is preferable that the separation rate be 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 that it be 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 contact agent that has come into contact with the pellets is separated through the separator, separating at least a portion of the cyclic dimers contained therein. By achieving a separation rate of 20% by mass or more, the accumulation of cyclic dimers in the contact agent can be suppressed, making it easier to obtain pellets of the desired quality. Furthermore, the separated cyclic oligomers can be supplied to esterification or polycondensation reaction processes and used as raw materials for polyester. It is a preferred method to return the separated cyclic oligomers to the esterification reaction tank in the esterification reaction process or to the slurry tank containing the dicarboxylic acid and diol components. The contact agent from which the cyclic oligomer has been separated may be used directly in the solvent contact process. If the contact agent is lost due to the separation of the cyclic oligomer, fresh contact agent can be replenished in the required amount as needed before being used in the solvent contact process.

[0095] As an example of a method for producing pellets of the polyester composition according to this disclosure, an example in which the "continuous" method (apparatus) is used in the solvent contact step (cyclic oligomer removal step) will be explained with reference to Figures 1 to 4. In the following example, a preferred embodiment of a method for producing pellets of a polyester composition containing polyester (PBSeT) made from sebaic acid as an aliphatic dicarboxylic acid component, terephthalic acid as an aromatic dicarboxylic acid component, 1,4-butanediol as a diol component, and trimethylolpropane as an optional polyfunctional compound will be described, but this disclosure is not limited to this embodiment.

[0096] Figure 1 is a schematic diagram illustrating one aspect of the manufacturing process (esterification reaction step) of polymer composition pellets, and Figure 2 is a schematic diagram illustrating one aspect of the manufacturing process (polycondensation step) of polymer composition pellets.

[0097] In Figure 1, the raw materials, sebacic 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 a solution of 1,4-butanediol, and then supplied to the catalyst supply line (3). Figure 1 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).

[0098] 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.

[0099] 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). On the other hand, 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 PBSeT) generated in the esterification reactor (A) is supplied to the first polycondensation reactor (a) shown in Figure 2 via the extraction pump (B) and the extraction line (4) for the esterified product.

[0100] In the process shown in Figure 1, 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).

[0101] 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 2, further diluted with BG, and then supplied to the esterification reaction product extraction line (4).

[0102] Next, the esterification reaction product, supplied from the esterification reaction product extraction line (4) through the filter (p) to the first polycondensation reactor (a), undergoes polycondensation under reduced pressure and is then supplied to the second polycondensation reactor (d) via the extraction gear pump (c), extraction line (L1), and filter (q). In the second polycondensation reactor (d), the polycondensation reaction proceeds further, usually at a lower pressure than in the first polycondensation reactor (a). The resulting polycondensate is supplied to the third polycondensation reactor (k) via the extraction gear pump (e), the extraction line (L3) which is the outlet channel, and filter (r). The third polycondensation reactor (k) is a horizontal reactor composed of multiple stirring blade blocks and equipped with two self-cleaning type stirring blades. The polycondensation product, introduced from the second polycondensation reactor (d) to the third polycondensation reactor (k) via the extraction line (L3), undergoes further polycondensation reaction there before being transferred to the pelletization process.

[0103] In the pelletizing process, the molten polymer composition is extracted into the atmosphere in the form of molten strands from the die head (g) via an extraction gear pump (m), an outlet filter (s), and an extraction line (L5). After being cooled with water or the like, it is cut by a rotary cutter (h) to form polymer pellets. Alternatively, the polymer can be extracted in strand form into water without being extracted into the atmosphere, and then cut by a rotary underwater cutter to form pellets.

[0104] In Figure 2, the labels (L2), (L4), and (L6) represent the vent lines of the first polycondensation reactor (a), the second polycondensation reactor (d), and the third polycondensation reactor (k), respectively. Filters (p), (q), (r), and (s) do not necessarily need to be installed in their entirety and can be installed as appropriate, taking into consideration the effectiveness of foreign matter removal and operational stability.

[0105] Figure 3 is a schematic diagram illustrating one aspect of the solvent contact process for polymer composition pellets and the separation process of cyclic dimers from the contact agent that has come into contact with the polymer composition pellets. The solvent is supplied from a circulation tank (I) to a treatment tank (III) via a solvent supply line (101) through a heat exchanger (II) with temperature control by a pump (IX). In the treatment tank (III), the solvent comes into contact with the pellets (e.g., countercurrent contact), 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). The contact agent supplied to the separator (XI) has the cyclic ester compound separated in the separator (XI), and is recovered to the circulation tank (I) via a contact agent extraction line (113). The separated cyclic ester compound is extracted to the outside through the cyclic ester compound extraction line (112). From the supply line (108), a fresh amount of contact agent is supplied that corresponds to the amount of contact agent extracted from the extraction line (112) along with the separated cyclic ester compound.

[0106] Pellets of the polymer composition to be subjected to contact treatment with the contact agent are continuously supplied from the pellet supply line (103), and after being subjected to contact treatment with the contact agent for a predetermined time, are continuously withdrawn from the pellet withdrawal line (104) while adjusting the withdrawal amount with a rotary valve (V). The contact agent withdrawn together with the treated pellets is separated in the pre-solid-liquid separator (VI), and after passing through the recovery tank (VII), is returned to the recovery line (106) via the contact agent supply line (105) by a pump (X). The continuously withdrawn treated pellets are separated from the accompanying contact agent in the pre-solid-liquid separator (VI), and then continuously supplied to the drying process located downstream of this separation process via the pellet withdrawal line 109, after passing through the solid-liquid separator (VIII).

[0107] Figure 4 is a schematic diagram illustrating one aspect 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 used as an example. After the solvent contact process, the treated pellets (pellets of the polyester composition according to this disclosure) are continuously supplied to the first drying tower (I) via a pellet supply line (201) connected to the extraction line 109 in Figure 4. 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 contact agent 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 sent from the first drying tower (I) to the cooling tower (J) via a rotary valve (O). Dry air is introduced into the cooling tower (J) from the cooling gas supply line (212) and released from the cooling gas extraction line (211).

[0108] 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 the pellet extraction line (204), rotary valve (P), and pellet supply line (205). Drying gas (usually air, for example) is supplied to the second drying tower (K) via the heat exchanger (S) and drying gas supply line (214), and is also discharged from the extraction line (213).

[0109] The dried pellets are continuously or intermittently extracted through 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. Note that in Figure 4, the process after the storage tank is not shown, but a second drying tower is also involved. (K) can also be used as a storage tank.

[0110] <Application> The polyester composition and its pellets obtained as described above, having a BSe1 content of less than 390 ppm by mass, are less likely to generate odor when subjected to injection molding or extrusion molding, significantly improving the working environment at molding sites such as injection molding and extrusion molding. Therefore, it becomes easier to use the polyester composition and its pellets in the mass production of biodegradable molded products. Furthermore, since injection molded and extruded molded products can be manufactured without generating odor, they are extremely useful as pellets for injection molding and extrusion molding.

[0111] <Molded products (injection molded products, extruded molded products)> The molding material for obtaining an injection-molded or extruded article may include at least the polyester composition according to this disclosure or its pellets, and may also include other materials, such as pellets made of other polymers, release agents, and other materials selected from the group. Injection-molded or extruded polymer pellets containing the polyester composition according to this disclosure can be obtained by molding them using a molding material containing the polyester composition according to this disclosure by injection molding or extrusion molding.

[0112] The shape of injection-molded or extruded articles can be any shape that can be molded by injection molding or extrusion molding. There are no limitations on the applications of injection-molded or extruded articles. 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, food packaging films) and agricultural films (agricultural mulch films). [Examples]

[0113] 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.

[0114] < Intrinsic viscosity (IV) dL / g > It was determined using an Ubbelohde viscometer in the following manner. That is, using a mixed solvent of phenol / tetrachloroethane (mass ratio 1 / 1), at a temperature of 30 °C, the dropping seconds of a polymer solution with a concentration of 0.5 g / dL and only the solvent were measured, and it was determined from the following calculation formula (3).

[0115] IV = ((1 + 4K H η sp ) 0.5 -1) / (2K H C) ··· (3) However, in calculation formula (3), η SP = η / η0 - 1, where η is the dropping seconds of the sample solution, η0 is the dropping seconds of the solvent, C is the sample solution concentration (g / dL), and K H is Huggins' constant. K H was adopted as 0.33.

[0116] <Calculation of the content of cyclic oligomers (BSe1, BS2) of polyester (HPLC analysis)> 0.5 g of polyester pellets was precisely weighed, 5 mL of chloroform was added, and after dissolving at room temperature, 35 mL of an ethanol / water mixed solution (volume ratio 4 / 1) was slowly dropped while stirring to precipitate the polymer component. After 15 minutes, stirring was stopped, and static separation was performed for 90 minutes. Next, 2 mL of the supernatant was collected, evaporated to dryness, and then 2 mL of acetonitrile was added and dissolved. After filtering through a filter with a pore size of 0.45 μm, using high performance liquid chromatography (trade name: Prominence, manufactured by Shimadzu Corporation), the mobile phase was started with acetonitrile / water (volume ratio = 4 / 6), and the composition was continuously changed to acetonitrile / water (volume ratio = 9 / 1) by the high-pressure gradient method for elution. The column was analyzed using an octadecylsilylated silica gel (ODS) column (trade 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.). Also, as the detector, a UV detector was used, and the detection wavelength was set to 210 nm. Using the obtained results, the cyclic oligomer component was quantified by the following method and expressed in mass ppm with respect to the pellets.

[0117] For the quantitative determination of the cyclic dimer (BS2), an absolute calibration curve method using pure BS2 was employed. Pure BS2 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 contact the oligomer component. After the contact treatment, the pellet was filtered off, and the acetone was evaporated from the acetone solution containing the oligomer component to obtain a solid. This solid was dissolved in acetone at 50°C to a saturated solution, then slowly cooled, the supernatant was discarded, and a needle-shaped precipitate was extracted. This recrystallization process was repeated several times for purification. This needle-shaped precipitate was confirmed to be BS2 by 1H-NMR analysis and high-performance liquid chromatography analysis. Cyclic oligomer components other than the cyclic dimer (BS2), such as BSe1, were identified by LC-MS analysis, and then quantified using the relative area value and factor of each oligomer component relative to the area value of BS2 in the chromatogram obtained by high-performance liquid chromatography.

[0118] Examples of quantitative calculation methods for the BS2 and BSe1 content are shown below. • BS2 content in pellets = Solution dilution ratio (40 in the above case) × (Slope of calibration curve × BS2 area value + Intercept of calibration curve) ÷ Pellet mass • BSe1 content in pellets = (BSe1 factor) × BS2 content in pellets × (BSe1 area value / BS2 area value) • Molecular weight per UV absorption per ester bond in BS2 = (Cyclic oligomer molecular weight: 344.4) / (Number of ester bonds: 4) = 86.1 • Molecular weight per UV absorption per ester bond in BSe1 = (Cyclic oligomer molecular weight: 256.4) / (Number of ester bonds: 2) = 128.2 • Factor of BSe1 = (Molecular weight per UV absorption per ester bond in BSe1) / (Molecular weight per UV absorption per ester bond in BS2) = 128.2 / 86.1 = 1.49

[0119] <Odor Sensory Test> Three grams of the polyester composition pellets to be evaluated were placed in an aluminum dish, covered with a lid, and the dish was placed on a hot plate heated to 230°C. After visually confirming that the pellets had completely melted and become transparent, five subjects brought their noses within approximately 3 cm of the dish and determined the odor intensity according to the following six-level odor intensity scale. <6-level odor intensity scale> 0 points: No odor detected. 1 point: The smell is finally detectable. 2 points: A faint odor that is recognizable as belonging to a specific entity. 3 points: Easily detectable odor. 4 points: Strong odor 5 points: Strong odor.

[0120] Then, using the judgment results based on the above 6-level odor intensity scale, the following evaluation criteria were used. <Evaluation Criteria> -: The worst rating is 0 or 1 point. +: The worst rating is 2 points. ++: The worst rating is 3 points. +++: The worst rating is 4 points, ++++: The worst rating is 5 points.

[0121] (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 stirring device, and 1500 parts by mass of anhydrous ethanol (purity 99% by mass 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 concentrated under reduced pressure using an evaporator in an oil bath at 60°C. After 1 hour, most of the ethanol had evaporated, 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 catalyst solution with a titanium atom content of 1.0% by mass.

[0122] [Production of pellets of polymer composition containing PBSSe (S / Se = 89 / 11 (molar ratio))] A reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, and vacuum port was supplied with 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, 0.125 parts by mass of trimethylolpropane, and 0.085 parts by mass of 1 wt% sodium hydroxide aqueous solution. The mixture was stirred and mixed to prepare a slurry. The molar ratio of succinic acid to sebacic acid was 89:11, and the ratio of the amount of 1,4-butanediol to the total amount of succinic acid and sebacic acid was 1.30. While stirring the contents of the vessel, nitrogen gas was introduced into the vessel, and the system was subjected to a nitrogen atmosphere by vacuum displacement. Next, the raw materials were dissolved at 160°C. After confirming that the raw materials were completely dissolved and the distillate temperature reached 50°C, the temperature was increased from 160°C to 230°C over 1 hour while stirring the system. The esterification reaction was then continued at 230°C and a pressure of 101 kPa for 1 hour. 0.80 parts by mass of the catalyst solution were added 5 minutes before the end of the esterification reaction. A PBSSe low polymer with an esterification rate of 98% was obtained.

[0123] The obtained PBSSe low polymer is transferred to a polycondensation reactor, where the temperature is raised from 230°C to 250°C over 30 minutes, while simultaneously undergoing a condensation process of 0.07 × 10⁻⁶ over 120 minutes. 3 The pressure was reduced to below Pa, and polymerization was continued while maintaining the heated, reduced pressure state. Polymerization was terminated when a predetermined stirring torque was reached, and the material was extruded in strand form into a water bath filled with cold water at around 10°C to solidify. After solidification, cylindrical pellets of the polymer composition containing PBSSe were obtained by cutting them using a strand cutter.

[0124] The pellets of the polymer composition described above were subjected to HPLC analysis according to the procedure described in the HPLC analysis section. Figure 5 shows the HPLC chromatogram obtained from the above HPLC analysis. In the HPLC chromatogram, a peak originating from BSe1, represented by structural formula (I), and a peak originating from BS2, represented by structural formula (II), were observed.

[0125] Next, the intrinsic viscosity of the polymer composition and the content of BSe1 and BS2 were calculated according to the method described above. The intrinsic viscosity of this polymer composition was 1.88 dL / g.

[0126] Next, 25 parts by mass of the polymer composition pellets and a contact treatment agent consisting of a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to the treatment tank and contacted at a temperature of 70°C for 1 hour (solvent contact step). After that, the treated pellets were dried under a nitrogen atmosphere at a temperature of 70°C. Pellet No. 1-1 was obtained. Furthermore, treated pellets No. 1-2 to 1-4 were obtained in the same manner as treated pellet No. 1-1, except that the contact time with the treatment solution was 2 hours, 5 hours, and 7 hours. For treated pellets No. 1-1 to 1-4, the intrinsic viscosity was measured, the BSe1 and BS2 content was calculated, and the odor was evaluated according to the method described above. The evaluation results for treated pellets No. 1-1 to 1-4, along with the evaluation results for the polymer composition (untreated) pellets, are shown in Table 5. In Table 5, "IV retention rate (%)" represents the percentage of the intrinsic viscosity of each treated pellet No. 1-1 to 1-4 relative to the intrinsic viscosity of the polymer composition.

[0127] [Table 5]

[0128] As shown in Table 5, treated pellets No. 1-1 to 1-4, which had a BSe1 content of less than 390 ppm by mass, exhibited reduced odor during heating compared to untreated pellets. Furthermore, since treated pellets No. 1-1 to 1-4 had a BS2 content of less than 3000 ppm by mass, it is considered that injection-molded and extruded articles obtained using these treated pellets exhibit reduced surface powdering.

[0129] (Example 2) Treated pellets No. 2-1 to 2-4 were obtained in the same manner as in Experimental Example 1, except that the contact treatment agent was replaced with a 50 vol% aqueous solution of ethanol. The obtained treated pellets No. 2-1 to 2-4 were evaluated in the same manner as in Example 1. The evaluation results for treated pellets No. 2-1 to 2-4, along with the evaluation results for untreated pellets, are shown in Table 6. Note that the data shown in Table 1 above are the results of this example.

[0130] [Table 6]

[0131] As shown in Table 6, treated pellets No. 2-1 to 2-4, which had a BSe1 content of less than 390 ppm by mass, exhibited reduced odor during heating and melting compared to untreated pellets. Furthermore, since treated pellets No. 2-1 to 2-4 had a BS2 content of less than 3000 ppm by mass, it is considered that injection-molded and extruded articles obtained using these treated pellets exhibit reduced surface powdering. Furthermore, Tables 5 and 6 show that each of the treated pellets No. 1-1 to 1-4 had a lower content of BSe1 and BS2 compared to the corresponding treated pellets No. 2-1 to 2-4. This indicates that using a higher concentration of ethanol aqueous solution as a contact agent is effective in obtaining polyester compositions with low content of BSe1 and BS2.

[0132] (Example 3) [Production of pellets of polymer composition containing PBSe (S / Se = 0 / 100 (molar ratio))] In the example of producing pellets of a polymer composition containing PBSSe according to Example 1, succinic acid was not used, and 78.9 parts by mass of sebacic acid, 45.7 parts by mass of 1,4-butanediol, 0.125 parts by mass of trimethylolpropane, 0.085 parts by mass of 1 wt% sodium hydroxide aqueous solution, and 0.80 parts by mass of catalyst solution were used, and the procedure was carried out in the same manner as above, except that the molar ratio of succinic acid to sebacic acid was 0:100, to obtain pellets of a polymer composition containing PBSSe.

[0133] The pellets of the polymer composition described above were subjected to HPLC analysis in the same manner as in Example 1. As a result, the obtained HPLC chromatogram showed a BSe1 peak, similar to that in Example 1. Next, the intrinsic viscosity and BSe1 content of the polymer composition were calculated according to the method described above. The intrinsic viscosity of this polymer composition was 1.76 dL / g.

[0134] Next, 25 parts by mass of the polymer composition pellets and a contact treatment agent consisting of a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to the treatment tank and contacted at a temperature of 50°C for 7 hours (solvent contact step). After that, the treated pellets were dried under a nitrogen atmosphere at a temperature of 60°C. I obtained No. 3-1. Furthermore, treated pellet 3-2 was obtained in the same manner as described above, except that the treatment temperature with the contact treatment agent was set to 25°C and the treatment time to 24 hours. For treated pellets No. 3-1 and 3-2, the intrinsic viscosity was measured, the BSe1 content was calculated, and the odor was evaluated according to the method described above. The evaluation results for treated pellets No. 3-1 to 3-2 are shown in Table 7, along with the evaluation results for the polymer composition (untreated) pellets. Note that the data described in Table 2 above are the results of this example.

[0135] [Table 7]

[0136] As shown in Table 7, treated pellet No. 3-2, which underwent the solvent contact process, was subjected to a low processing temperature of 25°C, which prevented sufficient removal of BSe1, resulting in the generation of a considerable odor during heating and melting. On the other hand, treated pellet No. 3-1 was subjected to a processing temperature of 50°C with the contact agent, which effectively removed BSe1 from the polymer composition pellets. As a result, a polyester composition according to this disclosure that does not easily generate odor during heating was obtained.

[0137] (Example 4) [Production of Pellet A-3 of a polymer composition containing PBSeT (Se / T = 46 / 54 (molar ratio))] In a reaction vessel equipped with a stirrer, nitrogen inlet, heater, thermometer, and vacuum port, 39.4 parts by mass of sebacic acid, 37.7 parts by mass of terephthalic acid, 57.1 parts by mass of 1,4-butanediol, 0.138 parts by mass of trimethylolpropane, 0.17 parts by mass of 1 wt% sodium hydroxide aqueous solution, and 0.71 parts by mass of a 3 wt% 1,4-butanediol solution of tetrabutoxytitanate were charged as raw materials. The molar ratio of sebacic acid to terephthalic acid was 46:54, and the ratio of the amount of 1,4-butanediol to the total amount of sebacic acid and terephthalic acid was 1.50. While stirring the contents of the container, nitrogen gas was introduced into the container, and the system was subjected to a nitrogen atmosphere by vacuum displacement. Next, the raw materials were dissolved at 160°C, and after confirming that the distillate temperature reached 50°C, the temperature was raised from 160°C to 230°C over 1 hour while stirring the system, and the esterification reaction was continued at 230°C and a pressure of 101 kPa for 2 hours. After confirming that terephthalic acid was uniformly dissolved, 0.70 parts by mass of the catalyst solution was added 5 minutes before the end of the esterification reaction. After the esterification reaction, the temperature was raised from 230°C to 250°C over 30 minutes, and at the same time, 0.07 × 10⁻⁶ parts were added over 85 minutes. 3 The pressure was reduced to below Pa, and polymerization was continued while maintaining the heated, reduced pressure state. Polymerization was terminated when a predetermined stirring torque was reached, and the material was extruded in strand form into a water bath filled with cold water at around 10°C to solidify. After solidification, cylindrical pellets of the polymer composition containing PBSeT were obtained by cutting them using a strand cutter. The resulting polymer composition pellets were subjected to HPLC analysis in the same manner as in Example 1. As a result, the obtained HPLC chromatogram showed a BSe1 peak, similar to that in Example 1. Next, the intrinsic viscosity of the polymer composition and the BSe1 content were calculated according to the method described above. The intrinsic viscosity of this polymer composition was 1.38 dL / g.

[0138] Next, 25 parts by mass of polymer composition pellets and a contact treatment agent consisting of a mixture of 80 parts by mass of ethanol and 20 parts by mass of water were continuously supplied to the treatment tank and contacted at a temperature of 70°C for 8 hours (solvent contact step). After that, the treated pellets were dried under a nitrogen atmosphere at a temperature of 60°C. o.4-1 was obtained. Furthermore, treated pellet 4-2 was obtained in the same manner as described above, except that the processing time was set to 5 hours. For treated pellets No. 4-1 and 4-2, the intrinsic viscosity was measured, the BSe1 content was calculated, and the odor was evaluated according to the method described above. The evaluation results for treated pellets No. 4-1 to 4-2 are shown in Table 8, along with the evaluation results for the polymer composition (untreated) pellets. Note that the data shown in Table 3 above are the results of this example.

[0139] [Table 8]

[0140] As shown in Table 8, treated pellet No. 4-2, which underwent the solvent contact process, had a processing time of 5 hours. Because the processing time was short, BSe1 could not be sufficiently removed, resulting in the generation of an odor during heating and melting. On the other hand, in processed pellet No. 4-1, the processing time was extended to 8 hours, which effectively removed BSe1 from the polymer composition pellets. As a result, a polyester composition according to this disclosure that does not easily generate an odor during heating was obtained.

[0141] (Reference example) [Manufacturing of pellets of polymer compositions 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 PBS low polymer with an esterification rate of 92%.

[0142] The PBS 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 into warm water adjusted to a temperature of 35°C from an outlet provided at the bottom of the polycondensation reactor, and immediately cut in the molten state to form flat, cocoon-shaped pellets with a mass of approximately 15 mg per pellet. The pellets were then held in the warm water for 1 minute while applying a linear velocity to the warm water (slow cooling step). Subsequently, the pellets were recovered from the hot water and dried. In this way, pellets of a polymer composition containing PBS were obtained. The pellets of the polymer composition described above were subjected to HPLC analysis in the same manner as in Example 1. Since PBS does not contain sebacic acid, the resulting HPLC chromatogram showed a BS2 peak, but no BSe1 peak. Furthermore, the odor of the polymer composition pellets was evaluated according to the method described above. As a result, all five subjects detected only a faint THF odor and did not detect any of the characteristic odor that is observed when polymer compositions containing polyester with sebacic acid unit A-1 are heated.< / pbset> < / pbsse> < / pbse>

Claims

1. A polyester composition comprising a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, The first constituent unit includes at least one constituent unit A-1 derived from sebacic acid, The second constituent unit includes at least one constituent unit B derived from 1,4-butanediol, A polyester composition wherein the content of the first cyclic ester compound represented by the following structural formula (I) in the polyester composition is 1 ppm by mass or more and less than 390 ppm by mass. 【Chemistry 1】

2. The polyester composition according to claim 1, wherein the content of the first cyclic ester compound is 350 ppm by mass or less.

3. The polyester composition according to claim 1, wherein the content of the first cyclic ester compound is 320 ppm by mass or less.

4. The polyester composition according to claim 1, wherein the proportion of the constituent unit A-1 in the first constituent unit is 4 mol% or more and 100 mol% or less.

5. The polyester composition according to claim 1, wherein the proportion of the constituent unit B in the second constituent unit is 10 mol% or more and 100 mol% or less.

6. The polyester composition according to claim 1, wherein the content of the second constituent unit relative to the total number of moles of the polyester constituent units is 49 mol% or more and 51 mol% or less.

7. The polyester composition according to claim 1, wherein at least one selected from the group consisting of the dicarboxylic acid and the diol is derived from biomass resources.

8. The polyester composition according to claim 1, wherein the bio-based carbon content determined by method B of ASTM D6866-18 is 0.1% or more and 100% or less.

9. The polyester composition according to claim 1, wherein the ratio of the constituent unit A-1 to the total number of moles of the constituent units of the polyester is 5 mol% or more.

10. The polyester composition according to claim 1, wherein the first constituent unit further comprises constituent unit A-2 derived from a dicarboxylic acid other than sebaic acid.

11. The polyester composition according to claim 10, wherein the constituent unit A-2 comprises at least one constituent unit selected from the group consisting of a constituent unit derived from succinic acid, a constituent unit derived from terephthalic acid, and a constituent unit derived from adipic acid.

12. Claim 11, wherein the constituent unit A-2 includes at least a constituent unit derived from succinic acid. The polyester composition described.

13. The polyester composition according to claim 12, wherein the content of the second cyclic ester compound represented by the following structural formula (II) in the polyester composition is less than 3,000 ppm by mass. 【Chemistry 2】

14. The polyester composition according to claim 12, wherein the polyester is poly(butylene succinate-sebacate).

15. The polyester composition according to claim 10, wherein the polyester comprises at least one polyester selected from the group consisting of poly(butylene succinate-sebacate) and poly(butylene sebacate-terephthalate).

16. The polyester composition according to claim 1, wherein the polyester comprises poly(butylene sebacate).

17. A pellet comprising the polyester composition according to any one of claims 1 to 16.

18. An injection-molded polymer pellet comprising at least the pellets described in claim 17.

19. An extruded polymer pellet comprising at least the pellets described in claim 17.

20. A method for producing the polyester composition according to claim 1, A step of obtaining a polymer composition containing the polyester by polycondensing a polymerization component that includes at least one selected from the group consisting of sebaciic acid and ester derivatives of sebaciic acid, and 1,4-butanediol. A step of obtaining pellets of the polymer composition, A method for producing a polyester composition, comprising the steps of: contacting pellets of the polymer composition with a contact treatment agent containing at least a water-soluble organic solvent to remove at least a portion of the first cyclic ester compound contained in the pellets of the polymer composition to obtain the polyester composition.

21. A method for producing the polyester composition according to claim 20, wherein the water-soluble organic solvent includes ethanol.

22. A polyester composition that reduces odor generation during melting, The polyester composition is The present invention relates to a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, wherein the polyester has a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, and the first structural unit is at least It also contains a constituent unit A-1 derived from sebacic acid, and the second constituent unit comprises at least 1, It contains constituent unit B derived from 4-butanediol, A polyester composition in which the generation of odor during melting is reduced by setting the content of the first cyclic ester compound represented by the following structural formula (I) in the polyester composition to 1 ppm by mass or more and less than 390 ppm by mass. 【Transformation 3】

23. A method for reducing the odor of a molten polyester composition, The polyester composition comprises a polyester having a first structural unit derived from a dicarboxylic acid and a second structural unit derived from a diol, wherein the first structural unit comprises at least structural unit A-1 derived from sebacic acid, and the second structural unit comprises at least structural unit B derived from 1,4-butanediol. The odor reduction method described above is: A method for reducing odor, comprising the step of setting the content of a first cyclic ester compound represented by the following structural formula (I) in the polyester composition to 1 ppm by mass or more and less than 390 ppm by mass. 【Chemistry 4】

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