Method for producing polyester resin composition and method for recovering germanium compound

Abstract

To provide a method for producing a polyester resin composition that can efficiently recover a germanium compound used as a polymerization catalyst, and a method for recovering the germanium compound.SOLUTION: A method for producing a polyester resin composition includes an esterification reaction process or a transesterification reaction process, and polycondensation reaction process as reaction processes. The method further includes a trapping process where distillate gas from any of the reaction processes is ventilated into liquid and / or mist-form ethylene glycol, and a process of reusing an ethylene glycol liquid (liquid A) discharged from the trapping process in the reaction processes. The germanium element content of the liquid A is 0.1 mass ppm or more and 5000 mass ppm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a polyester resin composition and a method for recovering a germanium compound. [Background technology]

[0002] Polyesters, such as polyethylene terephthalate (PET), are produced by the esterification reaction of terephthalic acid with ethylene glycol or the transesterification reaction of dimethyl terephthalate with ethylene glycol, followed by a polycondensation reaction of the resulting polyester oligomer in the presence of a polycondensation catalyst. To improve reactivity, ethylene glycol is supplied in excess relative to the terephthalic acid or dimethyl terephthalate. Most of the catalysts and additives used in each reaction also use ethylene glycol as a solvent, resulting in an excess of ethylene glycol present in the polycondensation reaction relative to the theoretical amount of ethylene glycol contained in the polyester. As a result, the excess ethylene glycol must be distilled off during the polycondensation reaction.

[0003] Antimony compounds, which are inexpensive and have excellent catalytic activity, are the most widely used polycondensation catalysts. However, when antimony compounds are used as catalysts, they tend to precipitate as insoluble metal particles during the PET manufacturing process, resulting in the generation of catalyst-derived impurities when the final PET is molded and processed. In recent years, the demand for high quality in optical films and release films has been increasing, and technology that can suppress the above-mentioned defects while maintaining mechanical and thermal properties is desired. Against this background, polyester manufacturing methods using germanium compounds instead of antimony compounds are being investigated.

[0004] When a germanium compound is used, the amount of germanium element remaining in the resulting polyester is significantly less than the amount added, and it disperses outside the reaction system. This results in a problem that the amount of germanium compound required for the polycondensation reaction is large, which increases the production cost of polyester. Furthermore, the germanium compound is distilled out of the reaction system together with ethylene glycol distilled during the polycondensation reaction, but only a portion of the germanium compound is present in the distilled ethylene glycol, making it difficult to recover all of the dispersed germanium compound.

[0005] To address these issues, studies have been carried out as shown in the following documents.

[0006] Patent Documents 1 and 2 disclose methods in which the distilled ethylene glycol that is generated is directly reused as a raw material.

[0007] Patent Document 3 discloses a method of recovering the catalyst by adsorbing the catalyst in the resulting distillate onto an adsorbent. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Unexamined Patent Publication No. 53-126096 [Patent Document 2] Japanese Patent Application Publication No. 55-110120 [Patent Document 3] Japanese Patent Application Laid-Open No. 2003-183374 Summary of the Invention [Problem to be solved by the invention]

[0009] Patent Documents 1 and 2 disclose methods for reusing the distillate generated in the polycondensation reaction, and Patent Document 3 discloses a method for recovering a catalyst in the distillate. However, both of these technologies relate to methods for utilizing the distillate, and the amount of germanium contained in the distillate is only a portion of the germanium compound that scatters, so the recovery rate is still low.

[0010] An object of the present invention is to provide a method for producing a polyester resin composition, which allows efficient recovery of a germanium compound serving as a polycondensation catalyst, and a method for recovering the germanium compound. [Means for solving the problem]

[0011] As a result of investigations aimed at solving the above problems, the present inventors have discovered a method for producing a polyester resin composition and a method for recovering a germanium compound, which are polycondensation catalysts, by passing the distillate gas generated in the reaction step through liquid and / or atomized ethylene glycol, and have arrived at the present invention.

[0012] The object of the present invention is achieved by the following means. (1) A method for producing a polyester resin composition having an esterification reaction or transesterification reaction step and a polycondensation reaction step as reaction steps, further comprising a trapping step of passing a distillate gas distilled in any of the reaction steps through liquid and / or atomized ethylene glycol, and a step of recycling the ethylene glycol liquid (Liquid A) discharged from the trapping step to the reaction steps, wherein the germanium element content of Liquid A is 0.1 ppm by mass or more and 5000 ppm by mass or less. (2) The method for producing a polyester resin composition according to (1), wherein the distillate gas is generated in a polycondensation reaction. (3) The method for producing a polyester resin composition according to (1), wherein the polycondensation reaction step is a step of carrying out the polycondensation reaction by adding a catalyst containing a germanium compound. (4) The method for producing a polyester resin composition according to (1), wherein the catalyst containing a germanium compound is germanium dioxide. (5) The method for producing a polyester resin composition according to (1), wherein the polyester is polyethylene terephthalate. (6) A method for producing a polyester resin composition, characterized in that in the step of reusing liquid A described in (1), the amount of elemental germanium contained in liquid A is managed and monitored, and the amount of elemental germanium supplied to the reaction system is controlled to be the required amount. (7) A method for recovering a germanium compound, comprising passing a distillate gas distilled in a process for producing a polyester resin composition through liquid and / or atomized ethylene glycol. (8) The method for recovering a germanium compound according to (7), wherein the ethylene glycol used for aeration is at a temperature of 0°C or higher and 100°C or lower. (9) The method for recovering a germanium compound according to (7), wherein the amount of ethylene glycol used for aeration is 0.1 L or more and 5 L or less per 1 kg of the polyester resin composition to be produced. (10) The method for recovering a germanium compound according to (7), wherein the polyester is polyethylene terephthalate. [Effects of the Invention]

[0013] The present invention provides a method for efficiently recovering a germanium compound, which is a polycondensation catalyst, and for producing a polyester resin composition containing less foreign matter derived from the catalyst element at low cost. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will be described in detail below. In the present invention, the term "element" may be used in the same sense as "atom."

[0015] The polyester resin composition in the present invention refers to a polyester resin obtained by polycondensation of a dicarboxylic acid component and a diol component.

[0016] As the dicarboxylic acid component in the present invention, various dicarboxylic acid components such as aromatic dicarboxylic acids, linear aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids can be used. Among them, aromatic dicarboxylic acids and their ester-forming derivative components are preferred from the viewpoints of mechanical properties, heat resistance, and hydrolysis resistance of the polyester resin composition. In particular, terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid, and their ester-forming derivative components are preferred from the viewpoints of polymerizability and mechanical properties.

[0017] Various diols can be used as the diol component in the present invention. Examples include aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, 2-methyl-1,3-propanediol, hexanediol, and neopentyl glycol; alicyclic diols such as cyclohexanedimethanol and cyclohexanediethanol; and aromatic diols such as bisphenol A, bisphenol S, styrene glycol, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, and 9,9'-bis(4-hydroxyphenyl)fluorene. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used.

[0018] Among these, diols with a boiling point of 230°C or less are preferred because they can be easily distilled out of the polymerization reaction system, and aliphatic diols are more preferred because they are low cost and highly reactive. Furthermore, ethylene glycol is particularly preferred from the viewpoint of the mechanical properties of the resulting polyester resin.

[0019] Incidentally, other dicarboxylic acid components, hydroxycarboxylic acid derivatives, and diol components may be copolymerized to the extent that the effects of the present invention are not impaired.

[0020] Next, a method for producing the polyester resin composition of the present invention will be described.

[0021] In the production method of the present invention, the esterification reaction step is a step in which a dicarboxylic acid and a diol are esterified at a predetermined temperature until a predetermined amount of water is distilled off to obtain a low polymer. When obtaining a low polymer by esterification, from the viewpoints of esterification reactivity and heat resistance, the molar ratio of dicarboxylic acid to diol (diol / dicarboxylic acid) before the start of the esterification reaction is preferably in the range of 1.05 to 1.40, more preferably 1.05 to 1.30, and even more preferably 1.05 to 1.20. By setting the ratio within this range, good reactivity is achieved, the production of by-products such as diol dimers can be suppressed, and good heat resistance can be achieved.

[0022] The transesterification reaction step is a step in which a dicarboxylic acid alkyl ester and a diol are transesterified until a predetermined amount of alcohol is distilled to obtain a low polymer. When a low polymer is obtained by the transesterification reaction, the molar ratio of the dicarboxylic acid alkyl ester to the diol (diol / dicarboxylic acid alkyl ester) is preferably in the range of 1.7 to 2.3 from the viewpoints of reactivity and heat resistance. By setting the ratio in this range, the transesterification reaction can be efficiently carried out and the by-production of diol dimers can be suppressed, thereby improving heat resistance.

[0023] The polycondensation reaction is a process for obtaining a polyester resin composition from a low polymer obtained by an esterification reaction or a transesterification reaction. Polyester polymers are synthesized by gradually increasing the temperature and vacuum within the range of 200 to 300°C and 0.05 to 30 kPa. While known polycondensation catalysts and co-catalysts can be used in the polycondensation reaction, a germanium compound is required. Antimony compounds, titanium compounds, and aluminum compounds can also be used in combination as polycondensation catalysts. The use of a germanium compound as a polycondensation catalyst reduces catalyst-induced contaminants in the resulting polyester resin composition, improving transparency and the quality of molded articles. Examples of germanium compounds include germanium dioxide, germanium ethoxide, and methylgermane. However, germanium dioxide is preferred from the viewpoint of suppressing the formation of contaminants. Germanium dioxide may be added directly to the reaction system, but it is preferable to use it as a solution in ethylene glycol or the like.

[0024] If necessary, manganese compounds, magnesium compounds, cobalt compounds, calcium compounds, phosphorus compounds, antioxidants, weathering agents, heat stabilizers, etc. may also be added.

[0025] In the production method of the present invention, it is necessary to pass the distillate gas distilled during one of the reaction steps through liquid and / or atomized ethylene glycol. This allows the germanium compound to be trapped and recovered in the ethylene glycol. "Liquid" refers to a liquid state such as that coming out of a shower or a state of bubbling in a liquid, while "atomized" refers to a mist state with finer droplets. A scrubber is preferably used for the trapping step. In the production of polyester resin compositions, the distillate gas is typically cooled and liquefied in a cooling device and stored in a storage tank. However, germanium compounds, which are prone to precipitation and solidification, solidify before the gaseous ethylene glycol contained in the distillate gas liquefies, and are lost from the distillate gas. This reduces the recovery rate of the germanium compound. In the present invention, the distillate gas is passed through liquid and / or atomized ethylene glycol to trap and recover the germanium compound before it solidifies.

[0026] The step of passing a gas through ethylene glycol may be carried out in any of the esterification reaction or transesterification reaction steps for producing a polyester resin composition, or the polycondensation reaction step. However, since a large amount of germanium compound is dispersed in the polycondensation reaction step, it is preferable to pass the distillate gas distilled in the polycondensation reaction step through ethylene glycol.

[0027] The ethylene glycol liquid (Liquid A) discharged from the trapping step must be reused in the reaction step. Reuse reduces the amount of newly added, very expensive germanium compounds. The germanium element content of Liquid A must be 0.1 mass ppm to 5,000 mass ppm, more preferably 2 mass ppm to 1,000 mass ppm, and even more preferably 10 mass ppm to 500 mass ppm. By keeping the germanium content below the upper limit, a polyester containing less germanium-derived impurities can be obtained when Liquid A is reused. Furthermore, a concentration lower than the lower limit requires high concentration when reused, which can result in the by-production of diol dimers and increased production costs.

[0028] In the process of reusing Liquid A, it is preferable to manage and monitor the amount of germanium element contained in Liquid A and control the amount of germanium element supplied to the reaction system. The amount of germanium element in Liquid A can be measured by, but is not limited to, ICP atomic emission spectroscopy. The amount of germanium element is preferably controlled by dilution or by adding a new germanium compound so that it is 3 to 500 ppm by mass relative to the weight of the polyester resin composition. The lower limit is preferably 5 ppm by mass or more. The upper limit is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less. Germanium compounds are used as polymerization catalysts for polyesters, and by using a concentration above the lower limit, the polycondensation reaction can proceed without delay. Furthermore, germanium element has excellent catalytic activity, and its excess presence contributes to thermal decomposition, oxidative decomposition, and hydrolysis of polyesters. Therefore, by maintaining the amount of germanium element at or below the upper limit, it is possible to suppress various decompositions of polyesters. Liquid A can also be reused in the reaction process after being appropriately diluted or concentrated as necessary.

[0029] The ethylene glycol used for aeration is preferably at a temperature of 0°C or higher and 100°C or lower. The upper limit is preferably 70°C or lower, more preferably 40°C or lower. By using ethylene glycol within the above range, the recovery rate of the germanium compound from the distillate gas is improved. Furthermore, if the temperature is lower than 0°C, the viscosity of the ethylene glycol increases, making it difficult to handle.

[0030] The amount of ethylene glycol used for aeration is preferably 0.1 L to 5 L per 1 kg of the polyester resin composition to be produced. It is more preferably 0.3 L to 3 L, and even more preferably 0.5 L to 2 L. By using an amount equal to or greater than the lower limit, a sufficient recovery rate of the germanium compound can be achieved. Furthermore, if the amount exceeds the upper limit, the amount of ethylene glycol used in the trapping step is large, and the germanium compound is diluted. This requires concentration for reuse, which results in the by-production of diol dimers and increases production costs.

[0031] The production method of the present invention can be applied to batch polymerization, semi-continuous polymerization, and continuous polymerization.

[0032] Specific examples of the method for producing the polyester resin composition of the present invention will be given below, but the present invention is not limited thereto.

[0033] A slurry of terephthalic acid and ethylene glycol (1.15 times the molar ratio of terephthalic acid) is gradually added from a slurry storage tank to an esterification reactor charged with bishydroxyethyl terephthalate (BHT) dissolved at 250°C, and the esterification reaction is allowed to proceed. The temperature within the reaction system is controlled to 245-250°C, and the esterification reaction is terminated when the reaction rate reaches 95%.

[0034] The esterification product thus obtained at 255°C is transferred to a polymerization apparatus, and a germanium compound is added. Then, phosphoric acid is added. During these operations, it is preferable to maintain the temperature in the system at 240 to 255°C so that the esterification product does not solidify.

[0035] Thereafter, the temperature inside the polymerization reactor is gradually increased to 290°C, while the pressure inside the polymerization reactor is gradually reduced from atmospheric pressure to 133 Pa or less. The distillate gas generated in the polycondensation reaction is passed through ethylene glycol at 30°C to trap the germanium compound. The ethylene glycol liquid discharged from the trapping step is supplied to the slurry storage tank and used as the raw ethylene glycol. The ethylene glycol liquid discharged from the trapping step may be reused as a catalyst solution.

[0036] The reaction is terminated when a predetermined stirring torque is reached, the reaction system is returned to normal pressure with nitrogen gas, and the molten polyester is discharged into cold water in the form of strands and cut to obtain a polyester resin composition. [Example]

[0037] The present invention will be described in more detail below with reference to examples. The physical properties in the examples were measured by the following methods.

[0038] (1) Germanium element (atom) content in Liquid A (unit: mass ppm) The sample was weighed, thermally decomposed with sulfuric acid, nitric acid, perchloric acid, and hydrofluoric acid, and then dissolved in dilute nitric acid to a constant volume. The germanium element (atomic) content in this solution was determined using ICP optical emission spectroscopy. The ICP optical emission spectroscopy used was a "PS3520VDDII" manufactured by Hitachi High-Tech Science Corporation.

[0039] (2) Germanium element (atom) content in polyester resin composition (unit: mass ppm) The weighed sample was thermally decomposed with sulfuric acid and nitric acid, and then dissolved in dilute nitric acid to a constant volume. The germanium element (atom) content in this solution was determined by ICP atomic emission spectroscopy in the same manner as in (1). The germanium element content in the polyester resin compositions in Tables 1 to 4 represents the amount of germanium element contained in 1 kg of PET.

[0040] (3) Germanium recovery rate In the production process of the polyester resin composition, the germanium recovery rate was calculated based on the following formula. The germanium element charge amounts in Tables 1 to 4 indicate the amount of germanium element charged when producing 1 kg of PET. A recovery rate of 60% or more was considered acceptable.

[0041]

number

[0042] (4) Evaluation of foreign matter in polyester resin compositions 0.1 mg of the polyester resin composition was sandwiched between two cover glasses and melted on a hot plate heated to 290°C to prepare a preparation on which a polymer thin film was formed. This preparation was observed under an optical microscope (Olympus Corporation: BX50, 400x magnification, dark field), and all observable light spots were counted. The number was used to make a rating, with C being a failure. A: 0~5 pieces / 0.1mg B: 6~9 pieces / 0.1mg C: 10 or more / 0.1mg.

[0043] (Reference example 1) A slurry consisting of 86 parts by weight of terephthalic acid and 37 parts by weight of ethylene glycol (1.15 times the molar ratio of terephthalic acid) was gradually added to an esterification reactor charged with 105 parts by weight of bishydroxyethyl terephthalate (hereinafter referred to as BHT) melted at 250°C, and the esterification reaction was allowed to proceed. The temperature in the reaction system was controlled to 245-250°C, and the esterification reaction was terminated when the reaction rate calculated from the amount of water distilled reached 95%.

[0044] 105 parts by weight (corresponding to 100 parts by weight of PET) of BHT was charged in a molten state from the esterification reactor to the polymerization apparatus, and the temperature was adjusted to 255°C. An ethylene glycol solution of manganese acetate tetrahydrate (23 ppm by mass as manganese element relative to the weight of the polyester resin composition) and germanium dioxide (45 ppm by mass as germanium element relative to the weight of the polyester resin composition) were added. Then, an ethylene glycol solution of phosphoric acid (38 ppm by mass as P element relative to the weight of the polyester resin composition) was added. The germanium dioxide was prepared by dissolving germanium dioxide in a 20% aqueous solution of tetraethylammonium hydroxide, followed by adding ethylene glycol to prepare an ethylene glycol solution.

[0045] Thereafter, the temperature inside the polymerization apparatus was gradually increased to 290°C, and the pressure was reduced from normal pressure to 133 Pa or less, and the polymerization reaction was carried out until a predetermined stirring torque was observed at 290°C. After completion of the polymerization reaction, the pressure inside the reaction system was returned to normal pressure with nitrogen gas, and the molten polyester inside the polymerization apparatus was discharged in the form of a strand into a water tank, cooled, and then cut to obtain a polyester resin composition in the form of pellets.

[0046] The distillate gas generated in the polycondensation reaction was vented into an ethylene glycol shower at 30°C using a scrubber to trap the germanium compound. 0.9 L of ethylene glycol was used for 1 kg of the polyester resin composition to be produced. The ethylene glycol liquid (Liquid Aa) discharged from the trapping step was recovered. Liquid Aa contained 27 ppm by mass of germanium element.

[0047] Example 1 The total amount of ethylene glycol raw material was designated as Liquid Aa, and an esterification reaction was carried out in the same manner as in Reference Example 1. Liquid Aa contained germanium, so that 7 ppm by mass of germanium element was added relative to the weight of the polyester resin composition at the time of the esterification reaction. Thereafter, a polyester resin composition was obtained in the same manner as in Reference Example 1, except that the amount of germanium dioxide added in the polymerization apparatus was changed to 38 ppm by mass of germanium element relative to the weight of the polyester resin composition.

[0048] The distillate gas generated in the polycondensation reaction was vented into an ethylene glycol shower at 30°C using a scrubber to trap the germanium compound. 0.9 L of ethylene glycol was used for 1 kg of the polyester resin composition to be produced. The ethylene glycol liquid (Liquid A) discharged from the trapping step was then recovered.

[0049] The amount of germanium element added, the conditions of the trapping step, and the contents of germanium element in the polyester resin composition and liquid A are summarized in Table 1.

[0050] [Table 1]

[0051] In Example 1, the germanium recovery rate was as high as 95%, and germanium was efficiently recovered by aeration with ethylene glycol.

[0052] Examples 2 to 4 A polyester resin composition was obtained in the same manner as in Example 1, except that the temperature of ethylene glycol used in the trapping step was changed as shown in Table 1.

[0053] In Example 2, the germanium recovery rate was also 90%, and germanium was recovered efficiently.

[0054] In Example 3, germanium could be efficiently recovered, but the temperature of ethylene glycol was close to its freezing point (-13°C), making it difficult to handle.

[0055] In Example 4, since the temperature of ethylene glycol was high, the efficiency of condensing the distillate gas was reduced, and the germanium recovery rate was slightly reduced.

[0056] (Examples 5 to 7) A polyester resin composition was obtained in the same manner as in Example 1, except that the amount of ethylene glycol used in the trapping step was changed as shown in Table 1.

[0057] In Example 5, the germanium recovery rate was also 93%, and germanium was recovered with high efficiency.

[0058] In Example 6, the amount of ethylene glycol used in the trapping step was small, which reduced the contact between the distillate gas and ethylene glycol, resulting in a slight decrease in the germanium recovery rate.

[0059] In Example 7, germanium was efficiently recovered, but a large amount of ethylene glycol was required in the trapping step.

[0060] (Examples 8 and 9) In Example 8, a scrubber was not used, and the distillate gas was bubbled into ethylene glycol in the trapping step. In Example 9, the distillate gas was passed through atomized ethylene glycol. Aside from these changes, a polyester resin composition was obtained in the same manner as in Example 1.

[0061] In both Examples 8 and 9, the germanium recovery rate was 90% or more, and germanium was recovered with high efficiency.

[0062] Examples 10 to 12 A polyester resin composition was obtained in the same manner as in Example 1, except that the amount of germanium element added in the reaction was changed as shown in Table 1 and the amount of ethylene glycol used in the trapping step was changed to 0.1 L.

[0063] In Examples 10 to 12, the amount of ethylene glycol used in the trapping step was 0.1 L, so the germanium recovery rate was lower than in Example 1, but germanium was recovered efficiently. However, because the germanium element content in Liquid A was high, a small amount of foreign matter was generated in the polyester resin composition obtained by reusing Liquid A (see Example 13). Furthermore, in Examples 11 and 12, the amount of germanium element added was high, and the excess germanium compound contributed to the decomposition reaction of the polyester, resulting in a slight decrease in quality.

[0064] (Comparative Example 1) A polyester resin composition was obtained in the same manner as in Example 1, except that the aeration step with ethylene glycol was omitted and the distillate gas was liquefied by contacting it with a cooling tube.

[0065] In Comparative Example 1, the distillate gas was liquefied in the cooling tube, so that germanium compounds were precipitated on the inner wall of the cooling tube, and the recovery rate of germanium from the liquefied ethylene glycol was low at 55%.

[0066] (Comparative Example 2) A polyester resin composition was obtained in the same manner as in Example 1, except that diantimony trioxide (70 ppm by mass as antimony element relative to the weight of the polyester resin composition) was added instead of germanium dioxide and polymerization was performed.

[0067] In Comparative Example 2, an antimony compound was used as the polycondensation catalyst, and therefore insoluble metal particles were precipitated, resulting in a poor quality of the resulting polyester resin composition.

[0068] (Comparative Example 3) Liquid Aa was diluted 3.5 times with fresh ethylene glycol, and using this as the ethylene glycol raw material, an esterification reaction was carried out in the same manner as in Reference Example 1. Since Liquid Aa contains germanium, 2 ppm by mass of germanium element was added relative to the weight of the polyester resin composition at the time of the esterification reaction. A polyester resin composition was obtained in the same manner as in Reference Example 1, except that germanium dioxide was not added to the polymerization apparatus.

[0069] The distillate gas generated in the polycondensation reaction was vented to an ethylene glycol shower at 30°C using a scrubber to trap the germanium compound. 6 L of ethylene glycol was used for venting per 1 kg of the polyester resin composition produced. The ethylene glycol liquid (Liquid A) discharged from the trapping step was then recovered.

[0070] The amount of germanium added was as low as 2 ppm by mass, so the target degree of polymerization was not achieved. In addition, the obtained polyester resin composition had poor heat resistance and produced foreign matter.

[0071] Example 13 The ethylene glycol liquid (Liquid A-12) recovered in Example 12 was mixed with fresh ethylene glycol, and using this as the ethylene glycol raw material, an esterification reaction was carried out in the same manner as in Reference Example 1. Since Liquid A-12 contains germanium, 455 ppm by mass of germanium element was added relative to the weight of the polyester resin composition at the time of the esterification reaction. A polyester resin composition was obtained in the same manner as in Reference Example 1, except that germanium dioxide was not added to the polymerization apparatus.

[0072] The distillate gas generated in the polycondensation reaction was vented into an ethylene glycol shower at 30°C using a scrubber to trap the germanium compound. 0.9 L of ethylene glycol was used for 1 kg of the polyester resin composition to be produced. The ethylene glycol liquid (Liquid A) discharged from the trapping step was then recovered. Table 2 shows the amount of germanium added, the trapping step conditions, and the germanium content in the polyester resin composition and Liquid A.

[0073] [Table 2]

[0074] The germanium recovery rate was high at 91%, but because the germanium content in Liquid A-12 was high, a small amount of foreign matter was generated in the polyester resin composition obtained by recycling.

[0075] (Reference example 2) A polyester resin composition was obtained in the same manner as in Reference Example 1, except that the amount of germanium dioxide added in the polymerization apparatus was changed to 2400 mass ppm in terms of germanium element relative to the weight of the polyester resin composition.

[0076] The distillate gas generated in the polycondensation reaction was vented into an ethylene glycol shower at 30°C using a scrubber to trap the germanium compound. 0.2 L of ethylene glycol was used for 1 kg of the polyester resin composition produced. The ethylene glycol liquid (Liquid Ab) discharged from the trapping step was recovered. Liquid Ab contained 5200 ppm of germanium element.

[0077] Comparative Example 4 The entire amount of the ethylene glycol raw material was used as Liquid Ab, and an esterification reaction was carried out in the same manner as in Reference Example 1. Liquid Ab contained germanium, so that at the time of the esterification reaction, 1404 mass ppm of germanium element was added relative to the weight of the polyester resin composition. A polyester resin composition was obtained in the same manner as in Reference Example 1, except that germanium dioxide was not added to the polymerization apparatus.

[0078] The distillate gas generated in the polycondensation reaction was vented into an ethylene glycol shower at 30°C using a scrubber to trap the germanium compound. 0.1 L of ethylene glycol was used for 1 kg of the polyester resin composition to be produced. The ethylene glycol liquid (Liquid A) discharged from the trapping step was then recovered. Table 3 shows the amount of germanium added, the trapping step conditions, and the germanium content in the polyester resin composition and Liquid A.

[0079] [Table 3]

[0080] The germanium content of the liquid Ab obtained in Reference Example 1 was as high as 5200 ppm by mass, and therefore the polyester resin composition obtained by recycling contained foreign matter.

[0081] Example 14 The liquid Aa obtained in Reference Example 1 was distilled and concentrated in a distillation apparatus capable of heating and stirring at a pressure of 15 kPa and a temperature of 150°C until the Ge element content became 7 wt%. The concentrated liquid Aa was added to a polymerization apparatus so that the germanium content was 45 mass ppm relative to the weight of the polyester resin composition. A polyester resin composition was obtained in the same manner as in Reference Example 1, except that germanium dioxide was not added to the polymerization apparatus.

[0082] The distillate gas generated in the polycondensation reaction was vented into an ethylene glycol shower at 30°C using a scrubber to trap the germanium compound. 0.9 L of ethylene glycol was used for 1 kg of the polyester resin composition produced. The ethylene glycol liquid (Liquid A) discharged from the trapping step was recovered. The results of Example 14 are shown in Table 4.

[0083] [Table 4]

[0084] In Example 14, even when the concentrated liquid of Liquid Aa was supplied to the polymerization apparatus and reused, the germanium recovery rate was 93%, and germanium was recovered efficiently.

Claims

1. A method for producing a polyester resin composition, which has an esterification reaction or transesterification reaction step, and a polycondensation reaction step as reaction steps, further comprising a trapping step of passing a distillate gas distilled in any of the reaction steps through liquid and / or atomized ethylene glycol, and a step of recycling the ethylene glycol liquid (Liquid A) discharged from the trapping step to the reaction step, wherein the germanium element content of Liquid A is 0.1 ppm by mass or more and 5000 ppm by mass or less.

2. 2. The method for producing a polyester resin composition according to claim 1, wherein the distillate gas is generated in a polycondensation reaction.

3. 2. The method for producing a polyester resin composition according to claim 1, wherein the polycondensation reaction step is a step of carrying out the polycondensation reaction by adding a catalyst containing a germanium compound.

4. 2. The method for producing a polyester resin composition according to claim 1, wherein the catalyst containing a germanium compound is germanium dioxide.

5. 2. The method for producing a polyester resin composition according to claim 1, wherein the polyester is polyethylene terephthalate.

6. A method for producing a polyester resin composition, characterized in that in the process of reusing liquid A described in claim 1, the amount of germanium element contained in liquid A is managed and monitored, and the amount of germanium element supplied to the reaction system is controlled to be the required amount.

7. A method for recovering a germanium compound, comprising passing a distillate gas distilled in a process for producing a polyester resin composition through liquid and / or atomized ethylene glycol.

8. 8. The method for recovering a germanium compound according to claim 7, wherein the ethylene glycol used for aeration has a temperature of 0°C or higher and 100°C or lower.

9. A method for recovering a germanium compound, wherein the amount of ethylene glycol used for aeration is 0.1 L or more and 5 L or less per 1 kg of the polyester resin composition to be produced.

10. 8. The method for recovering a germanium compound according to claim 7, wherein the polyester is polyethylene terephthalate.

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