Polyester resin and method for producing polyester resin

Abstract

The object of this invention is to provide a polyester resin with a reduced number of foreign matter particles. [Solution] The present invention relates to a polyester resin made from a diol composition mainly composed of ethylene glycol, wherein the diol composition satisfies the following condition (I). 0.01 ≤ q ≤ 20.0 (I) However, q = c + e c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm)

Description

[Technical Field]

[0001] This invention relates to polyester resin and a method for producing polyester resin. [Background technology]

[0002] Traditionally, polyester resins, such as polyethylene terephthalate resin, have been widely used in films, fibers, bottles, and other applications due to their excellent mechanical strength, chemical stability, gas barrier properties, aroma retention, and hygiene, as well as their relatively low cost. In recent years, particularly in film applications, there has been a demand for polyester resins suitable for high-speed film formation to improve productivity. However, with high-speed film formation, problems such as deterioration of smoothness during melt extrusion and film breakage have arisen. One of the contributing factors to these problems is the presence of foreign matter in the polyester resin.

[0003] For example, Patent Document 1 focuses on foreign matter originating from catalyst residue and describes how adjusting the amount and order of addition of various metal compounds added as catalysts during polycondensation can reduce foreign matter without degrading the color. Patent Document 2 proposes a polyester resin with a low volume resistivity (ρV) to improve productivity and describes how adjusting the content of specific metal atoms can lower the volume resistivity without causing foreign matter. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2003-321538 [Patent Document 2] Japanese Patent Publication No. 2016-188352 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when using polyester resins obtained with conventional technology, the reduction in the number of foreign particles was not sufficient for applications requiring superior film-forming properties and smoothness, such as optical applications, and further improvements were needed.

[0006] Therefore, in order to solve the problems of the conventional technology, the inventors of this invention proceeded with research aimed at providing a polyester resin with a reduced number of foreign matter particles. [Means for solving the problem]

[0007] Examples of specific embodiments of the present invention are shown below.

[0008] [1] A polyester resin made from a diol composition mainly composed of ethylene glycol, A polyester resin whose diol composition satisfies the following condition (I). 0.01 ≤ q ≤ 20.0 (I) However, q = c + e c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka] [2] The polyester resin according to [1], wherein the diol composition satisfies the following condition (II). 0.01 ≤ r ≤ 50.0 (II) However, r = a + c + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [Chemical Formula] [3] The polyester resin according to [1] or [2], wherein the diol composition satisfies the following condition (III). 0.01≦s≦70.0 (III) Provided that s=a+b+c+d+e a=(mass concentration of the compound represented by the following formula (1) / 148.16) / (mass concentration of ethylene glycol / 62.07) (mole ppm) b=(mass concentration of the compound represented by the following formula (2) / 148.16) / (mass concentration of ethylene glycol / 62.07) (mole ppm) c=(mass concentration of the compound represented by the following formula (3) / 134.13) / (mass concentration of ethylene glycol / 62.07) (mole ppm) d=(mass concentration of the compound represented by the following formula (4) / 120.10) / (mass concentration of ethylene glycol / 62.07) (mole ppm) e=(mass concentration of the compound represented by the following formula (5) / 166.17) / (mass concentration of ethylene glycol / 62.07) (mole ppm) [Chemical Formula] [4] The polyester resin according to any one of [1] to [3], wherein the content (a) of the compound represented by the following formula (1) in the diol composition is 30 mole ppm or less. Provided that a=(mass concentration of the compound represented by the following formula (1) / 148.16) / (mass concentration of ethylene glycol / 62.07) (mole ppm) [Chemical Formula] [5] The polyester resin according to any one of [1] to [4], wherein the content (e) of the compound represented by the following formula (5) in the diol composition is 15 mole ppm or less. Provided that e=(mass concentration of the compound represented by the following formula (5) / 166.17) / (mass concentration of ethylene glycol / 62.07) (mole ppm) [ka] [6] The polyester resin according to any one of [1] to [5], wherein the diol composition contains diethylene glycol, and the content of diethylene glycol per 100 moles of ethylene glycol is 150 moles ppm or less. [7] The polyester resin according to any one of [1] to [6], wherein the specific gravity of the diol composition is 1.1120 to 1.1140. [8] Volume resistivity (ρV) is 10 × 10 7 A polyester resin described in any of [1] to [7], having a value of Ω·cm or less. [9] When a film with a thickness of 50 μm is made, 1 m of film 2 A polyester resin according to any one of [1] to [8], wherein the number of granular particles with a particle size of 25 μm or larger present per unit is 1700 or less.

[10] A polyester resin according to any of [1] to [9], for use in the manufacture of polyester film.

[11] A polyester film formed from the polyester resin described in any of [1] to

[10] .

[12] The polyester film described in

[11] for use in optical components.

[13] A method for producing a polyester resin using a diol composition mainly composed of a dicarboxylic acid component and ethylene glycol as raw materials, A method for producing a polyester resin, wherein the diol composition satisfies the following condition (I). 0.01 ≤ q ≤ 20.0 (I) However, q = c + e c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[14] A method for producing a polyester resin according to

[13] , wherein the diol composition satisfies the following condition (II). 0.01 ≤ r ≤ 50.0 (II) However, r = a + c + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[15] A method for producing a polyester resin according to

[13] or

[14] , wherein the diol composition satisfies the following condition (III). 0.01 ≤ s ≤ 70.0 (III) However, s = a + b + c + d + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) b = (Mass concentration of the compound represented by formula (2) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) d = (mass concentration of the compound represented by formula (4) below / 120.10) / (mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[16] A method for producing a polyester resin according to any one of

[13] to

[15] , wherein the polyester resin is produced by at least an esterification step or a transesterification step and a polycondensation step. [Effects of the Invention]

[0009] According to the present invention, a polyester resin with a reduced number of foreign matter particles can be obtained. [Modes for carrying out the invention]

[0010] The present invention will be described in detail below. The following description may be based on representative embodiments and specific examples, but the present invention is not limited to such embodiments. In this specification, when "X~Y" (where X and Y are any numbers) is used, unless otherwise specified, it includes the meaning of "X or greater and Y or less," as well as "preferably greater than X" or "preferably less than Y." Also, when "X or greater" (where X is any number) or "Y or less" (where Y is any number) is used, it also includes the intention that "preferably greater than X" or "preferably less than Y." In the following description, "film" and "sheet" are not clearly distinguished, and the term "film" may include "sheet," and vice versa.

[0011] (Polyester resin) This embodiment relates to a polyester resin (hereinafter also referred to as "this polyester resin") made from a diol composition mainly containing ethylene glycol, wherein the diol composition satisfies the following condition (I). 0.01 ≤ q ≤ 20.0 (I) However, q = c + e c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[0012] Furthermore, this embodiment relates to a polyester resin made from a diol composition mainly containing ethylene glycol, wherein the diol composition satisfies the following condition (II). 0.01 ≤ r ≤ 50.0 (II) However, r = a + c + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[0013] Furthermore, this embodiment relates to a polyester resin made from a diol composition mainly composed of ethylene glycol, wherein the diol composition satisfies the following condition (III). 0.01 ≤ s ≤ 70.0 (III) However, s = a + b + c + d + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) b = (Mass concentration of the compound represented by formula (2) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) d = (mass concentration of the compound represented by formula (4) below / 120.10) / (mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[0014] The mass concentrations of ethylene glycol and the compounds of formulas (1) to (5) in the diol composition are measured using gas chromatography.

[0015] The conditions for gas chromatography are as follows: Gas chromatography: Agilent Technologies 7890 Detector: Flame Ion Detector (FID) Analysis Column: DB-WAX UI Column inner diameter: 0.25 mm Column length: 30m Column film thickness: 0.25 μm Heating conditions: 100°C (2 minutes) → 10°C / min → 240°C (9 minutes) Inlet temperature: 230℃ Detector temperature: 260℃ Carrier gas: Helium 1 mL / min Injection mode: Split 10:1 Sample injection volume: 1 μL Retention time: Diethylene glycol: 12.0 min Compounds having the structure of formula (1): 12.6 minutes Compounds having the structure of formula (2): 12.7 minutes Compound having the structure of formula (3): 14.1 minutes Compounds having the structure of formula (4): 14.4 minutes Compound having the structure of formula (5): 23.8 minutes

[0016] The correspondence between the retention times and the compounds in formulas (1) to (5) above is determined using GC-MS, specifically by electron ionization (EI) and chemical ionization (CI). Furthermore, the sensitivity of diethylene glycol in ethylene glycol, obtained from gas chromatography measurements, is corrected for the number of carbon atoms and functional groups. The concentration of ethylene glycol is similarly determined by quantitative analysis of a standard sample. From the mass concentrations of the compounds (1) to (5) calculated using the method described above, the molar proportions (a, b, c, d, e) of the compounds (1) to (5) in the diol composition relative to ethylene glycol are calculated using the following formulas: [Formula A], [Formula B], [Formula C], [Formula D], and [Formula E]. [Equation A] a = (Mass concentration of the compound represented by Equation (1) / 148.16) / (Mass concentration of ethylene glycol / 62.07) [Equation B] b = (Mass concentration of the compound represented by Equation (2) / 148.16) / (Mass concentration of ethylene glycol / 62.07) [Equation C] c = (Mass concentration of the compound represented by Equation (3) / 134.13) / (Mass concentration of ethylene glycol / 62.07) [Equation D] d = (Mass concentration of the compound represented by Equation (4) / 120.10) / (Mass concentration of ethylene glycol / 62.07) [Equation E] e = (Mass concentration of the compound represented by Equation (5) / 166.17) / (Mass concentration of ethylene glycol / 62.07)

[0017] The correspondence between the retention time and each acetal compound can be identified using GCMS (gas chromatography-mass spectrometry) by electron ionization (EI) and chemical ionization (CI). The sensitivity of diethylene glycol in ethylene glycol is corrected for the number of carbon atoms and functional groups, and a FID relative mass sensitivity of 0.95 for diethylene glycol is used. The concentration of diethylene glycol is quantified using a standard sample. From the obtained concentrations, the mass concentrations of the compounds of chemical formulas (1) to (5) are calculated by applying the FID relative mass sensitivity correction shown in Table 1 below, as described in Modern Chemistry Series 11 Chromatography (3rd edition), Tokyo Kagaku Dojin, p111, Table 7.7 (1981).

[0018] [Table 1]

[0019] In this embodiment, the number of granular particles (foreign matter) present in the polyester resin can be reduced by specifying the content of a particular compound in the diol composition used as a raw material. Furthermore, in this embodiment, a polyester resin with excellent color tone and suppressed yellowness can be obtained. Thus, since the polyester resin of this embodiment is manufactured from the above raw materials, a polyester resin with fewer foreign matter and excellent color tone can be obtained. For this reason, this polyester resin is useful for the manufacture of polyester films, and is particularly preferably used for the manufacture of optical films.

[0020] The number of granular particles (foreign matter) in this polyester resin is calculated based on the amount of film produced from this polyester resin, specifically the amount per meter of film with a thickness of 50 μm. 2 This is the number of granular particles (foreign matter) with a particle size of 25 μm or larger present per unit area. 2 The number of granular particles with a particle size of 25 μm or larger per unit area is preferably 1700 or less, more preferably 1600 or less, even more preferably 1500 or less, and particularly preferably 1400 or less. 2 The lower limit of the amount of foreign matter is preferable, where the number of granular particles with a particle size of 25 μm or larger per unit area is small. The lower limit of the number of foreign matter is usually 0 or more, but it may also be 10 or more. By keeping the number of granular particles below the above upper limit, the smoothness of the film can be improved, and the productivity of the film can be increased more effectively.

[0021] To measure the number of granular particles (foreign matter) in this polyester resin, first, 10 kg of the polyester resin sample is crystallized and dried in a hot air dryer at 160°C for 4 hours to reduce the moisture content to 100 ppm or less. Then, using a 20 mm diameter single-screw extruder, the resin is melt-extruded at a resin temperature of 285°C and an extrusion speed of 8 kg / hour to obtain a film with a thickness of 50 μm and a width of 100 mm from a 150 mm T-die. Next, after confirming the film thickness range by focusing on the front and back surfaces of the film, an image processing device is used to capture images by focusing and scanning from the front to the back surface in grayscale image accumulation input mode. The maximum value of the straight-line distance between two points on the periphery of the particles recognized by the image processing device is defined as the maximum diameter, and the number of particles with a maximum diameter of 25 μm or more is counted. This operation is repeated three times in different fields of view. The average value of the obtained counts is taken as 1 m 2 This is converted to a unit per film area. The shape of the foreign matter to be counted may be any shape, such as rod-shaped, layered, flaky, spherical, or elliptical.

[0022] The granular substances (foreign matter) in this polyester resin are thought to be generated when certain acetal compounds react during esterification or polycondensation, either existing as oligomers or forming cross-linked structures.

[0023] The b-value of this polyester resin is preferably 0 to 2.6, and more preferably 0 to 2.5. If the b-value of this polyester resin is within the above range, it can be determined that it is a polyester resin with excellent color tone and suppressed yellowing.

[0024] To measure the b-value of this polyester resin, the polyester resin is filled into a cylindrical powder colorimeter cell with an inner diameter of 36 mm and a depth of 15 mm, and the color coordinate b-value of Hunter's color difference formula in the Lab color system, as described in Reference 1 of JIS Z8730:2009, is measured using a colorimeter (ZE-6000 manufactured by Nippon Denshoku Industries Co., Ltd.).

[0025] The intrinsic viscosity (IV) of this polyester resin is preferably 0.45 dL / g or higher, more preferably 0.50 dL / g or higher, even more preferably 0.55 dL / g or higher, and even more preferably 0.60 dL / g or higher. Furthermore, the viscosity of this polyester resin is preferably 0.80 dL / g or lower, more preferably 0.75 dL / g or lower, and even more preferably 0.70 dL / g or lower. Setting the intrinsic viscosity of the polyester resin to be above the lower limit above improves stability during film formation. On the other hand, setting the intrinsic viscosity to be below the upper limit above is preferable because it has the advantage of making it easier to suppress excessive pressure increase in the film-forming extruder. The intrinsic viscosity of the polyester resin is measured at 30°C using a viscosity (IV) measuring device after accurately weighing 1 g of polyester resin, dissolving it in 100 mL of a mixed solvent of phenol / tetrachloroethane = 50 / 50 (mass ratio).

[0026] The acid value (number of terminal carboxyl groups: AV) of this polyester resin is preferably 35 eq / t or less, more preferably 30 eq / t or less, and particularly preferably 25 eq / t or less. Furthermore, the number of terminal carboxyl groups (AV) of this polyester resin is preferably 15 eq / t or more. By having the number of terminal carboxyl groups (AV) of the polyester resin within the above range, a resin and molded articles with excellent heat resistance can be obtained.

[0027] The acid value (number of terminal carboxyl groups: AV) of polyester resin is calculated using the following formula. Terminal carboxyl group weight (eq / t) = (AB) × 0.01 × f × 1000 / W Here, A is the volume (ml) of 0.01N sodium hydroxide benzyl alcohol solution required for titration, B is the volume (ml) of 0.01N sodium hydroxide benzyl alcohol solution required for blank titration, W is the volume (g) of the resin sample, and f is the titer of the 0.01N sodium hydroxide benzyl alcohol solution.

[0028] The volume resistivity (ρV) of this polyester resin is 10 × 10 7Ω·cm or less is preferred, more preferably 7.5×10 7 Ω·cm or less, further preferably 5.0×10 7 Ω·cm or less. In addition, the volume resistivity (ρV) of the present polyester resin is preferably 0.1×10 7 Ω·cm or more, more preferably 0.5×10 7 Ω·cm or more, further preferably 1×10 7 Ω·cm or more. When the volume resistivity of the polyester resin is within the above range, the adhesion to the cooling drum during film formation is improved, the film formation speed can be increased, and the productivity can be enhanced.

[0029] When measuring the volume resistivity (ρV) of the present polyester resin, first, 23 g of the polyester resin sample is placed in a side-arm test tube with an inner diameter of 20 mm and a length of 180 mm, and the inside of the tube is sufficiently purged with nitrogen. Thereafter, the test tube is immersed in an oil bath at 160°C, and the inside of the tube is vacuum-dried for 4 hours at 1 Torr or lower using a vacuum pump. Next, the temperature of the oil bath is raised to 295°C to melt the resin sample, and then nitrogen pressure restoration and pressure reduction are repeated to remove mixed bubbles. Into this melt, two stainless steel electrode plates with an area of 1 cm 2 are inserted in parallel at an interval of 5 mm (the non-opposing back surfaces are covered with an insulator), and after the temperature stabilizes, a DC voltage of 100 V is applied between the electrodes using a resistance meter ("MODEL HP4339B" manufactured by Hewlett-Packard Company), and the volume resistivity (Ω·cm) is determined from the resistance value at that time.

[0030] (Raw Material) (Diol Composition) The diol composition used in the present embodiment is a composition containing ethylene glycol as a main component. In the diol composition, "containing ethylene glycol as a main component" means that ethylene glycol accounts for 50 mol% or more of all diol components, preferably 85 mol% or more, more preferably 90 mol% or more, and particularly preferably 95 mol% or more. When the proportion of ethylene glycol is not less than the above lower limit, a polyester resin excellent in practical use in terms of mechanical strength, gas barrier properties, and heat resistance as a molded article can be obtained.

[0031] In this embodiment, the diol composition satisfies the following condition (I). 0.01 ≤ q ≤ 20.0 (I) However, q = c + e c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[0032] In condition (I), q (moles in ppm) should be 20.0 or less, preferably 15.0 or less, more preferably 10.0 or less, even more preferably 5.0 or less, and particularly preferably 2.5 or less. A smaller q is preferable, but the lower limit is usually 0.01 or higher, and may be 0.05 or higher. The value of q defines the proportion of linear acetal (formaldehyde acetal), and by setting the value of q within the above range, a polyester resin with fewer impurities can be obtained.

[0033] Furthermore, the diol composition preferably satisfies the following condition (II). 0.01 ≤ r ≤ 50.0 (II) However, r = a + c + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[0034] In condition (II), r (moles in ppm) should be 50.0 or less, preferably 30.0 or less, more preferably 20.0 or less, even more preferably 10.0 or less, and particularly preferably 5.0 or less. A smaller r is preferable, but the lower limit is 0.01 or more, and it may also be 0.05 or more. By setting the value of r within the above range, a polyester resin with fewer impurities and a suppressed yellowish tint with excellent color tone can be obtained.

[0035] Furthermore, the diol composition is preferably satisfied with the following condition (III). 0.01 ≤ s ≤ 70.0 (III) However, s = a + b + c + d + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) b = (Mass concentration of the compound represented by formula (2) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) c = (Mass concentration of the compound represented by formula (3) below / 134.13) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) d = (mass concentration of the compound represented by formula (4) below / 120.10) / (mass concentration of ethylene glycol / 62.07) (moles in ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) [ka]

[0036] In condition (III), s (moles in ppm) should be 70.0 or less, preferably 60.0 or less, more preferably 50.0 or less, even more preferably 25.0 or less, even more preferably 10.0 or less, and particularly preferably 8.0 or less. A smaller s is preferable, but the lower limit is usually 0.01 or more, and may be 0.1 or more. By setting the value of s within the above range, a polyester resin with fewer impurities and a suppressed yellowish tint with excellent color tone can be obtained.

[0037] The compounds represented by formulas (1) to (5) above are acetal compounds or intermediates consisting of an aldehyde compound (acetaldehyde, formaldehyde, glycolaldehyde, etc.) and ethylene glycol. Hereafter, these compounds may be collectively referred to as "acetal compounds." The quantitative analysis method for the compounds represented by formulas (1) to (5) is as described above.

[0038] Acetal compounds, which are by-reaction organisms during the synthesis of ethylene glycol, were thought to be a cause of yellowing in polyester resins and affect their color tone. The inventors of this invention have diligently investigated this matter and discovered that certain acetal compounds also contribute to an increase in impurities in polyester resins. This is presumed to be because certain acetal compounds react during esterification or polycondensation reactions, existing as oligomers or forming cross-linked structures, thus becoming impurities. In other words, in this invention, we focus not only on impurities originating from metal catalyst residues but also on specific acetal compounds as causes of impurities. By controlling the values ​​of q, r, and / or s, calculated from the amount of each acetal compound in the diol composition used as a raw material, to specific values, it is possible to obtain a polyester resin with fewer impurities.

[0039] In this embodiment, one method for controlling the values ​​of q, r, and / or s, which are calculated from the amounts of each acetal compound in the diol composition used as a raw material, is to use a diol composition derived from exhaust gas or synthesis gas. In particular, it is preferable to use a diol composition derived from exhaust gas emitted during coal combustion. Furthermore, the values ​​of q, r, and / or s can also be controlled by employing a purification process to remove formaldehyde, acetal compounds, etc., when obtaining the diol composition.

[0040] In this embodiment, the diol composition is preferably satisfied with the following condition (IV). 0.01 ≤ t ≤ 15.0 (IV) However, t = a + b + d a = (Mass concentration of the compound represented by equation (1) / 148.16) / (Mass concentration of ethylene glycol / 62.07) (moles in ppm) b = (mass concentration of the compound represented by equation (2) / 148.16) / (mass concentration of ethylene glycol / 62.07) (moles in ppm) d = (mass concentration of the compound represented by equation (4) / 120.10) / (mass concentration of ethylene glycol / 62.07) (moles in ppm)

[0041] In condition (IV), t (moles in ppm) should be 15.0 or less, preferably 10.0 or less, and more preferably 5.0 or less. A smaller t is preferable, but the lower limit is usually 0.01 or higher, and may also be 0.05 or higher. By setting the value of t within the above range, the proportion of cyclic acetal compounds can be controlled, and as a result, it becomes easier to obtain a polyester resin with fewer impurities and a superior color tone with suppressed yellowing.

[0042] In this embodiment, the content (a) of the compound represented by formula (1) per 100 moles of ethylene glycol in the diol composition is preferably 50 moles ppm or less, more preferably 40 moles ppm or less, even more preferably 30 moles ppm or less, even more preferably 15 moles ppm or less, even more preferably 10 moles ppm or less, and particularly preferably 5 moles ppm or less. Furthermore, the content (a) of the compound represented by formula (1) per 100 moles of ethylene glycol in the diol composition is preferably as low as possible, but the lower limit is usually 0.01 moles ppm or more, and may also be 0.05 moles ppm or more. By setting the content (a) of the compound represented by formula (1) to be below the upper limit, the yellow discoloration of the resulting polyester resin can be suppressed, and the number of foreign matter particles can also be suppressed.

[0043] In this embodiment, the content (b) of the compound represented by formula (2) per 100 moles of ethylene glycol in the diol composition is preferably 9 moles ppm or less, more preferably 7 moles ppm or less, even more preferably 5 moles ppm or less, even more preferably 4 moles ppm or less, even more preferably 3 moles ppm or less, and particularly preferably 2 moles ppm or less. Furthermore, the content (b) of the compound represented by formula (2) per 100 moles of ethylene glycol in the diol composition is preferably as low as possible, but the lower limit is usually 0.01 moles ppm or more, and may be 0.05 moles ppm or more. By setting the content (b) of the compound represented by formula (2) to be below the upper limit, the yellow discoloration of the resulting polyester resin can be suppressed, and the number of foreign matter particles can also be suppressed.

[0044] In this embodiment, the content (c) of the compound represented by formula (3) per 100 moles of ethylene glycol in the diol composition is preferably 10.0 mol ppm or less, more preferably 5.0 mol ppm or less, even more preferably 3.0 mol ppm or less, even more preferably 2.5 mol ppm or less, and even more preferably 2.0 ppm or less. Furthermore, while a smaller content (c) of the compound represented by formula (3) per 100 moles of ethylene glycol in the diol composition is preferable, the lower limit is usually 0.01 mol ppm or more, and may also be 0.05 mol ppm or more. By setting the content (c) of the compound represented by formula (3) to be below the upper limit, the number of foreign matter in the resulting polyester resin can be suppressed.

[0045] In this embodiment, the content (d) of the compound represented by formula (4) per 100 moles of ethylene glycol in the diol composition is preferably 10.0 mol ppm or less, more preferably 5 mol ppm or less, even more preferably 2.5 mol ppm or less, preferably 2.0 mol ppm or less, more preferably 1.5 mol ppm or less, even more preferably 1.0 mol ppm or less, and particularly preferably 0.9 mol ppm or less. Furthermore, while a smaller content (d) of the compound represented by formula (4) per 100 moles of ethylene glycol in the diol composition is preferable, the lower limit is usually 0.01 mol ppm or more, and may be 0.05 mol ppm or more. By setting the content (d) of the compound represented by formula (4) to be below the upper limit, the yellow discoloration of the resulting polyester resin can be suppressed, and the number of foreign matter particles can also be suppressed.

[0046] In this embodiment, the content (e) of the compound represented by formula (5) per 100 moles of ethylene glycol in the diol composition is more preferably 30 moles ppm or less, even more preferably 15 moles ppm or less, even more preferably 10 moles ppm or less, particularly preferably 5 moles ppm or less, and even more preferably 2.5 ppm or less. Furthermore, the content (e) of the compound represented by formula (5) per 100 moles of ethylene glycol in the diol composition is preferable as it is small, but the lower limit is usually 0.01 moles ppm or more, and may be 0.05 moles ppm or more. By setting the content (e) of the compound represented by formula (5) to be below the upper limit, the number of foreign matter in the resulting polyester resin can be suppressed.

[0047] In this embodiment, the diol composition may contain diethylene glycol. The content of diethylene glycol per 100 moles of ethylene glycol in the diol composition is preferably 150 moles ppm or less, more preferably 100 moles ppm or less, even more preferably 50 moles ppm or less, and even more preferably 45 moles ppm or less. The lower the diethylene glycol content, the better, and the lower limit is usually 0 moles, and it may also be 0.01 moles ppm. By keeping the diethylene glycol content below the above upper limit, the thermal stability and mechanical properties of the polyester resin can be improved.

[0048] The diol composition may contain other diol components besides ethylene glycol and acetal compounds. Examples of other diol components include aliphatic diols such as diethylene glycol, 1,4-butanediol, trimethylene glycol, pentamethylene glycol, hexamethylene glycol, octamethylene glycol, decamethylene glycol, neopentyl glycol, and 2-ethyl-2-butyl-1,3-propanediol; alicyclic diols such as 1,2-cyclohexanediol, 1,4-cyclohexanediol, 1,1-cyclohexanedimethylol, 1,4-cyclohexanedimethylol, and 2,5-norbornanedimethylol; and xylylene. Aromatic diols such as lycole, 4,4'-dihydroxybiphenyl, 2,2-bis(4'-hydroxyphenyl)propane, 2,2-bis(4'-β-hydroxyethoxyphenyl)propane, bis(4-hydroxyphenyl)sulfone, and bis(4-β-hydroxyethoxyphenyl)sulfonic acid; and polyethers such as diethylene glycol, polyethylene glycol, polytetramethylene ether glycol, and ethylene oxide adducts or propylene oxide adducts of 2,2-bis(4'-hydroxyphenyl)propane; are examples. Multiple other diol components may be used in combination.

[0049] Furthermore, the diol composition may contain biomass-derived diols or diol components obtained through chemical recycling. The diol composition may also contain, for example, biomass-derived ethylene glycol.

[0050] In the diol composition, the content of 2-methanol,1,3-dioxolane per 100 moles of ethylene glycol is preferably 50 moles ppm or less, more preferably 25 moles ppm or less, and even more preferably 10 moles ppm or less. In this embodiment, it is preferable that the diol composition contains substantially no 2-methanol,1,3-dioxolane, and the content of 2-methanol,1,3-dioxolane relative to ethylene glycol may be 0 moles.

[0051] In this embodiment, at least a portion of the diol composition distilled from the polyester manufacturing process may be recovered and reused as a diol raw material. In this case, the diol composition mentioned above is a composition that also includes the recycled raw material, and it is preferable that the composition including the recycled raw material satisfies the above-mentioned conditions.

[0052] In this embodiment, the specific gravity of the diol composition is preferably 1.1120 to 1.1140, and more preferably 1.1125 to 1.1135, from the viewpoint of manufacturing efficiency and control of the physical properties (number of foreign matter, etc.) of the resulting polyester resin. By setting the specific gravity of the diol composition within the above range, yellow discoloration of the resulting polyester resin can be suppressed, and the number of foreign matter can also be suppressed.

[0053] (Dicarboxylic acid component) The dicarboxylic acid component used in this embodiment contains a dicarboxylic acid and / or an ester derivative of a dicarboxylic acid. Examples of dicarboxylic acid components include aromatic dicarboxylic acids such as terephthalic acid, phthalic acid, isophthalic acid, dibromoisophthalic acid, sodium sulfisophthalate, phenylenedioxydicarboxylic acid, 4,4'-diphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylketonedicarboxylic acid, 4,4'-diphenoxyethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, and 2,6-naphthalenedicarboxylic acid; alicyclic dicarboxylic acids such as hexahydroterephthalic acid and hexahydroisophthalic acid; and aliphatic dicarboxylic acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecadicarboxylic acid, and dodecadicarboxylic acid. Examples of ester derivatives of dicarboxylic acids include alkyl esters having 1 to 6 carbon atoms.

[0054] As the dicarboxylic acid component, a dicarboxylic acid component obtained by chemical recycling may be used. Examples of such dicarboxylic acid components include dimethyl terephthalate, terephthalic acid, isophthalic acid, and bis(2-hydroxyethyl) terephthalate.

[0055] In particular, in this embodiment, it is preferable to use a diol composition mainly composed of ethylene glycol and a dicarboxylic acid component mainly composed of terephthalic acid and / or dimethyl terephthalate as raw materials.

[0056] (Other copolymer components) In this embodiment, as copolymer components other than the diol composition and dicarboxylic acid component described above, one or more of the following may be used: for example, hydroxycarboxylic acids and alkoxycarboxylic acids such as glycolic acid, p-hydroxybenzoic acid, and p-β-hydroxyethoxybenzoic acid; monofunctional components such as stearyl alcohol, heneicosanol, octacosanol, benzyl alcohol, stearic acid, behenic acid, benzoic acid, t-butylbenzoic acid, and benzoylbenzoic acid; and trifunctional or polyfunctional components such as tricarbaryl acid, trimellitic acid, trimesic acid, pyromellitic acid, naphthalenetetracarboxylic acid, gallic acid, trimethylolethane, trimethylolpropane, glycerol, pentaerythritol, and sugar esters.

[0057] (Method of manufacturing polyester resin) This embodiment relates to a method for producing a polyester resin using a diol composition mainly composed of a dicarboxylic acid component and ethylene glycol as raw materials (hereinafter also referred to as "the method for producing this polyester resin"). The diol composition used in this embodiment preferably satisfies the above-mentioned condition (I), more preferably satisfies the above-mentioned condition (II), and even more preferably satisfies the above-mentioned condition (III). Examples of diol compositions used in this embodiment include the above-mentioned diol compositions, and the preferred embodiments are similar.

[0058] In the manufacturing method of this embodiment, the polyester resin is preferably manufactured through at least an esterification step or a transesterification step and a polycondensation step. Furthermore, in this embodiment, the method for manufacturing the polyester resin includes a step of recovering at least a portion of the diol composition distilled from the manufacturing step and a step of purifying the recovered diol composition, and the purified diol composition may be reused as part of the raw material. For example, in this embodiment, the method may include a step of recovering at least a portion of the diol composition distilled from at least one step selected from the group consisting of an esterification step, a transesterification step and a polycondensation step, and a step of purifying the recovered diol composition.

[0059] (Esterification process / Transesterification process) The esterification step is a process in which an esterification reaction is carried out using an esterification reactor, with the diol composition and dicarboxylic acid component as raw materials. The transesterification step is a process in which a transesterification reaction is carried out using an esterification reactor (transesterification reactor), with the diol composition and dicarboxylic acid component as raw materials, in the presence of a transesterification catalyst. Specifically, the raw materials, the diol composition and dicarboxylic acid component, are subjected to an esterification or transesterification reaction in an esterification reactor under reduced pressure to increased pressure and heating. During this process, excess diol composition and water produced by the reaction are distilled off while the esterification or transesterification reaction is carried out to obtain an oligomer, which is a low molecular weight polyester.

[0060] The esterification reaction is carried out using a single esterification reactor or a multi-stage reactor in which multiple esterification reactors are connected in series. In this reaction, the esterification reaction is carried out while refluxing the diol composition and removing the water and excess diol composition produced in the reaction from the system. The esterification reaction is preferably carried out until the esterification reaction rate (the percentage of all carboxyl groups of the starting material dicarboxylic acid that react with the diol component and are esterified) reaches 90% or more, preferably 93% or more. Furthermore, the number-average molecular weight of the oligomer obtained as the esterification reaction product is preferably 500 to 5000.

[0061] Esterification reactors used for esterification or transesterification reactions typically have a heat transfer jacket for temperature control, but it is preferable to have a heat transfer coil inside the reactor to facilitate temperature control. Alternatively, an external circulation line (external circulation line) may be provided to circulate the oligomer and heat it in a heat exchanger. The esterification reactor may also be equipped with a stirring device, and conventionally known stirring blades such as anchor blades, paddle blades, and Faudler blades can be used. Furthermore, a reflux condenser may be provided to return the distillate to the reactor. In this embodiment, a method of returning the distillate to the reactor is preferred for the purpose of reducing the heat load.

[0062] The conditions for the esterification and / or transesterification reaction are arbitrary as long as the reaction can proceed, and the reaction temperature is usually 120°C or higher, preferably 150°C or higher. The reaction temperature is usually 300°C or lower, preferably 250°C or lower, and more preferably 210°C or lower. The reaction time is usually 2 to 9 hours, preferably 2 to 7 hours, and more preferably 2 to 5 hours.

[0063] For esterification and / or transesterification reactions, the reaction conditions are as follows: In the case of a single esterification reactor, the temperature is usually around 190-280°C, the pressure is usually around 0-400 kPaG (where kPaG represents relative pressure to atmospheric pressure), and the reaction time is usually 1-10 hours with stirring. In the case of multiple esterification reactors, the reaction temperature in the first esterification reactor is usually 240-270 kPaG, the reaction temperature in the final stage is usually 120-250°C, preferably 150-210°C, and the relative pressure to atmospheric pressure is usually 0-150 kPaG, preferably 0-130 kPaG.

[0064] (Polycondensation process) In the polycondensation process, the esterified product (oligomer) obtained in the esterification and / or transesterification process described above is subjected to melt polycondensation. The polycondensation reactor used for the polycondensation process is usually equipped with a heat transfer jacket for temperature control, but a heat transfer coil may be provided inside the polycondensation reactor to facilitate temperature control. The polycondensation reactor is usually equipped with a stirring device with a vertical or horizontal centerline. As stirring blades, conventionally known types such as anchor blades, paddle blades, and Faudler blades can be used in the case of a stirring device with a vertical centerline, and spectacle blades and wheel blades can be used in the case of a stirring device with a horizontal centerline.

[0065] The reaction temperature during the polycondensation reaction is preferably 320°C or lower, and more preferably 300°C or lower. Furthermore, the reaction temperature during the polycondensation reaction is preferably 200°C or higher, and more preferably 270°C or higher. When the reaction temperature is below the above upper limit, the thermal decomposition reaction during manufacturing is suppressed, and the color tone of the polyester resin tends to improve. Also, when the reaction temperature is above the above lower limit, the polycondensation reaction proceeds more efficiently.

[0066] The lower the pressure inside the reaction vessel during the polycondensation reaction, the easier the reaction proceeds. In the final stage, the pressure is preferably 27 kPa or less, more preferably 20 kPa or less, and even more preferably 13 kPa or less. In particular, it is preferable to maintain a pressure of 0.4 kPa or less in at least one of the polycondensation reaction vessels.

[0067] The time required for the polycondensation reaction is adjusted to maintain a constant intrinsic viscosity of the resulting polyester resin, but is typically 2 to 12 hours, preferably 2 to 10 hours. When the polycondensation reaction is carried out continuously, the average residence time in the polycondensation reaction tank is considered the time required for the polycondensation reaction.

[0068] Melt polycondensation is carried out in a single reactor or a reactor consisting of multiple reactors connected in series. For example, melt polycondensation is carried out in a multi-stage reactor consisting of a fully mixed reactor with a stirring blade as the first stage, and horizontal plug-flow reactors with stirring blades as the second and third stages, while distilling the diol composition produced out of the system under reduced pressure. In the case of a single reactor, the temperature is usually around 250 to 290°C, the pressure is gradually reduced from atmospheric pressure to a final pressure of usually around 1.3 to 0.0013 kPa, and the reaction time is 1 to 20 hours under stirring. In the case of multiple reactors, the reaction temperature in the first reactor is usually 220 to 310°C, preferably 225 to 290°C, and the pressure is usually 1.3 to 65 kPa, preferably 2 to 26 kPa. Furthermore, the reaction temperature in the final stage is typically 265 to 320°C, preferably 270 to 300°C, and the pressure is typically 0.013 to 1.3 kPa, preferably 0.065 to 0.65 kPa.

[0069] Examples of polycondensation catalysts used in the polycondensation process include antimony compounds, germanium compounds, aluminum compounds, titanium compounds, phosphorus compounds, and magnesium compounds. Among these, it is preferable to use at least one selected from antimony compounds, titanium compounds, magnesium compounds, and phosphorus compounds, more preferably antimony compounds or titanium compounds, and even more preferably titanium compounds. By using the above-mentioned compounds, particularly titanium compounds, as the polycondensation catalyst, it is possible to reduce the amount of polycondensation catalyst added, thereby making it easier to suppress the generation of foreign matter originating from the polycondensation catalyst.

[0070] The amount of polycondensation catalyst used is typically 1 to 400 ppm by mass, preferably 1 to 150 ppm by mass, more preferably 1 to 80 ppm by mass, and more preferably 1 to 20 ppm by mass, relative to the resulting polyester resin, in terms of metal atoms. In addition, phosphorus compounds such as orthophosphoric acid, orthophosphoric acid alkyl esters, ethyl acid phosphate, triethylene glycol acid phosphate, phosphorous acid, and phosphorous acid alkyl esters can be used as stabilizers in the polycondensation step. The amount used is preferably 1 to 1000 ppm by mass, and more preferably 2 to 200 ppm by mass, relative to the resulting polyester resin.

[0071] (Solid phase polymerization process) The polyester resin obtained in the polycondensation process is usually extracted in strand form from an outlet at the bottom of the polycondensation tank, and then cut with a cutter while or after water cooling to form pellets or other granular materials. The pellets can be further polymerized to a higher degree by performing solid-phase polycondensation as needed.

[0072] Solid-phase polycondensation reactions are carried out under an inert gas atmosphere such as nitrogen, under reduced pressure, or under an inert gas flow. The reaction temperature for solid-phase polycondensation is usually 150°C or higher, preferably 200°C or higher, while it is usually 270°C or lower, preferably 220°C or lower. Solid-phase polycondensation reactions are carried out for a relatively long time until the desired intrinsic viscosity is reached. The reaction time for solid-phase polycondensation is usually 100 hours or less, preferably 6 to 80 hours. Solid-phase polycondensation can be carried out in batch or continuous manner.

[0073] (Collection and Recycling Process) In the recovery and reuse process, first, the distillates distilled from the above-described process are recovered. Typically, in the esterification and / or transesterification process, an equivalent or greater amount of diol component is added to the dicarboxylic acid component in order to allow the dicarboxylic acid component to react sufficiently. For this reason, it is preferable to distill off any excess diol composition in the polycondensation process that follows the esterification and / or transesterification process as the reaction progresses.

[0074] The distillate contains ethylene glycol, which is part of the diol composition, as well as acetal compounds produced as by-products. The distillate also contains water produced by the esterification reaction or C1-C4 alcohols, acetaldehyde, etc., produced by the transesterification reaction. Furthermore, among the components contained in the distillate from the esterification reaction step, substances with lower boiling points than ethylene glycol, such as water or C1-C4 alcohols, may be present as gases in the distillate.

[0075] At least a portion of the surplus diol composition distilled from the above process may be used as is, but it is preferable that it be reused as a raw material diol composition after undergoing a purification process. When reusing, it is preferable to supply the surplus diol composition alone or mixed with the diol composition received as a raw material to the slurrying process, esterification process, or transesterification process.

[0076] When purifying an excess diol composition, the purification process involves separating impurities from the distillate produced in each step by methods such as filtration, distillation, and adsorption, and then purifying and recovering ethylene glycol and acetal compounds. These purification methods may be used individually or in combination as appropriate. In particular, when a step for purifying the diol composition is included, it is preferable to employ a method that combines filtration and distillation. Specifically, first, solid impurities in the ethylene glycol are removed using a metal filter or filter cloth, and then, in a distillation column, the mixture is heated above the boiling point of ethylene glycol, and high-boiling point impurities are separated by drawing them out from the bottom of the column while refluxing as necessary, and ethylene glycol is distilled out at the top of the column. By using such an ethylene glycol purification process, various acetal compounds contained in ethylene glycol can be efficiently separated. The ethylene glycol purification process may further include a method in which low-boiling point impurities in the ethylene glycol are separated by distillation at the top of the column in a separate distillation column, and ethylene glycol is drawn out from the bottom of the column and recovered. In particular, if the method includes separating low-boiling point impurities by distillation at the top of the column, it is even more preferable because heating ethylene glycol in the presence of water converts the acetal compounds contained in ethylene glycol into glycolaldehyde and diethylene glycolaldehyde and ethylene glycol, and the resulting aldehydes can be separated by distillation.

[0077] The diol composition to be reused preferably satisfies the above-mentioned condition (I), more preferably satisfies the above-mentioned condition (II), and even more preferably satisfies the above-mentioned condition (III).

[0078] (Polyester film) This embodiment relates to a polyester film formed from the polyester resin described above. By using the polyester resin described above, a polyester film with excellent transparency can be obtained. In the polyester resin of this embodiment, the number of granular materials (foreign matter) is suppressed, so even when the film formation speed of the polyester film is increased, problems such as deterioration of smoothness or film breakage during melt extrusion of the film are suppressed. As a result, a polyester film with excellent film formation properties, as well as heat resistance and durability, can be obtained. Furthermore, since the polyester film of this embodiment has excellent color tone, it can be used for optical components, general industrial materials, window films, or packaging materials, and is particularly preferred for use in optical components.

[0079] The polyester film may be a single layer or a laminated structure of two or more layers. If the polyester film is a laminated structure, it may be a multilayer structure of four or more layers, in addition to a two-layer or three-layer structure.

[0080] The polyester film may be an unoriented film (sheet) or an oriented film, but it is preferably an oriented film, and more preferably a biaxially oriented film.

[0081] The thickness of the polyester film is not particularly limited as long as it is within the range that allows it to be formed as a film, but from the viewpoint of mechanical strength, handling, and productivity, it is preferably in the range of 5 to 300 μm, more preferably 10 to 125 μm.

[0082] (Method of manufacturing polyester film) A method for manufacturing a polyester film preferably includes the step of extruding dried polyester resin pellets from a die as a molten sheet using an extruder, and then cooling and solidifying it with a cooling roll to obtain an unstretched sheet. In this case, it is preferable to improve the adhesion between the sheet and the rotating cooling drum in order to improve the flatness of the sheet, and electrostatic application adhesion and / or liquid coating adhesion methods are preferably employed.

[0083] Next, the obtained unstretched sheet is stretched in one direction using a roll or tenter type stretcher. The stretching temperature is usually 70 to 120°C, preferably 80 to 110°C, and the stretching ratio is usually 2.5 to 7 times, preferably 3 to 6 times. Then, it is stretched in a direction perpendicular to the first stretching direction, usually at 70 to 170°C, with a stretching ratio of usually 2.5 to 7 times, preferably 3 to 6 times. Subsequently, heat treatment is performed at a temperature of 180 to 270°C under tension or under relaxation of 30% or less to obtain a biaxially oriented film. In the above stretching, a method can also be adopted in which stretching in one direction is performed in two or more stages. In that case, it is preferable that the final stretching ratios in both directions are within the above ranges.

[0084] Furthermore, simultaneous biaxial stretching can also be used for the production of polyester film. Simultaneous biaxial stretching is a method in which an unstretched sheet is simultaneously stretched and oriented in the machine direction and width direction under temperature control, usually at 70 to 120°C, preferably 80 to 110°C, with a stretching ratio of usually 4 to 50 times, preferably 7 to 35 times, and more preferably 10 to 25 times in area ratio. Subsequently, heat treatment is performed at a temperature of 170 to 270°C under tension or under relaxation of 30% or less to obtain a stretched and oriented film. Regarding the simultaneous biaxial stretching apparatus employing the above stretching method, conventionally known stretching methods such as screw type, pantograph type, and linear drive type can be used. [Examples]

[0085] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist of the invention. Next, the various measurement methods used in the following examples are shown.

[0086] (Determination of compounds in formulas (1) to (5)) The mass concentrations of ethylene glycol and compounds of formulas (1) to (5) in the diol composition were measured using gas chromatography.

[0087] [Gas chromatography conditions] Gas chromatography: Agilent Technologies 7890 Detector: Flame Ion Detector (FID) Analysis Column: DB-WAX UI Column inner diameter: 0.25 mm Column length: 30m Column film thickness: 0.25 μm Heating conditions: 100°C (2 minutes) → 10°C / min → 240°C (9 minutes) Inlet temperature: 230℃ Detector temperature: 260℃ Carrier gas: Helium 1 mL / min Injection mode: Split 10:1 Sample injection volume: 1 μL Retention time: Diethylene glycol: 12.0 min Compounds having the structure of formula (1): 12.6 minutes Compounds having the structure of formula (2): 12.7 minutes Compound having the structure of formula (3): 14.1 minutes Compounds having the structure of formula (4): 14.4 minutes Compound having the structure of formula (5): 23.8 minutes

[0088] The correspondence between the retention times and the compounds in formulas (1) to (5) was determined using GC-MS, specifically by electron ionization (EI) and chemical ionization (CI). Furthermore, the sensitivity of diethylene glycol in ethylene glycol, obtained from gas chromatography measurements, was corrected for the number of carbon atoms and functional groups. The concentration of ethylene glycol was similarly determined by quantitative analysis of the standard. From the mass concentrations of the compounds (1) to (5) calculated using the method described above, the values ​​of a, b, c, d, and e (molars in ppm) were calculated using the following equations: [Equation A], [Equation B], [Equation C], [Equation D], and [Equation E]. [Equation A] a = (Mass concentration of the compound represented by Equation (1) / 148.16) / (Mass concentration of ethylene glycol / 62.07) [Equation B] b = (Mass concentration of the compound represented by Equation (2) / 148.16) / (Mass concentration of ethylene glycol / 62.07) [Equation C] c = (Mass concentration of the compound represented by Equation (3) / 134.13) / (Mass concentration of ethylene glycol / 62.07) [Equation D] d = (Mass concentration of the compound represented by Equation (4) / 120.10) / (Mass concentration of ethylene glycol / 62.07) [Equation E] e = (Mass concentration of the compound represented by Equation (5) / 166.17) / (Mass concentration of ethylene glycol / 62.07)

[0089] (Measurement of intrinsic viscosity (IV)) 0.25 g of polyester resin sample was dissolved in a phenol / tetrachloroethane (mass ratio 1 / 1) mixed solvent at 110°C for 30 minutes to a concentration (c) of 1.0 g / dL. Then, the viscosity was measured at 30°C using an Ubbelohde capillary tube. The relative viscosity (η) with respect to the solvent was calculated from the solvent passage time (t0) and the solution passage time (t) using the following formula. rel ) was sought. η rel = t / t0 From the relative viscosity, the specific viscosity (η) can be derived from the following equation. sp ) was sought. η sp =η rel -1 Furthermore, the specific viscosity is divided by the concentration (c) to obtain the reduced viscosity (η) at a concentration (c) of 1.0 g / dL. sp / c The reduced viscosity was calculated for concentrations (c) of 0.5 g / dL, 0.2 g / dL, and 0.1 g / dL. The intrinsic viscosity (IV) (dL / g) was then calculated by extrapolating concentration (c) to 0 from these values.

[0090] (color tone) A polyester resin sample was filled into a cylindrical powder colorimeter with an inner diameter of 36 mm and a depth of 15 mm. Using a colorimeter (ZE-6000, manufactured by Nippon Denshoku Industries Co., Ltd.), the color coordinate b value of the Hunter color difference formula in the Lab color system, as described in Reference 1 of JIS Z8730:2009, was determined by the simple average of the values ​​measured at four locations by rotating the measurement cell by 90 degrees each time using the reflection method.

[0091] (Acid value (AV): Amount of terminal carboxyl groups) After grinding the polyester resin sample, it was dried in a hot air dryer at 140°C for 15 minutes and then cooled to room temperature in a desiccator. 0.1 g of the cooled sample was accurately weighed and placed in a test tube. 3 mL of benzyl alcohol was added, and the sample was dissolved at 195°C for 3 minutes while blowing in dry nitrogen gas. Then, 5 mL of chloroform was gradually added, and the mixture was cooled to room temperature. 1-2 drops of phenol red indicator were added to this solution, and the solution was titrated with a 0.1 N sodium hydroxide solution of benzyl alcohol while stirring and blowing in dry nitrogen gas. The titration was stopped when the color changed from yellow to red. A blank sample was also prepared by performing the same procedure without the polyester resin sample, and the amount of terminal carboxyl groups was calculated using the following formula (3). Terminal carboxyl group weight (eq / t) = (AB) × 0.1 × f / W … (3) A: Amount of 0.1N sodium hydroxide benzyl alcohol solution required for titration (μL) B: Volume (μL) of 0.1N sodium hydroxide benzyl alcohol solution required for titration of the blank. W: Amount of sample (g) f: Titer of a 0.1N sodium hydroxide solution in benzyl alcohol

[0092] The titer (f) of the 0.1N sodium hydroxide benzyl alcohol solution was calculated by the following method. First, 5 mL of methanol was taken into a test tube while blowing dry nitrogen gas into it, 1-2 drops of phenol red ethanol solution were added as an indicator, and the mixture was titrated with 0.4 mL of 0.1N sodium hydroxide benzyl alcohol solution until the color change point. Next, 0.2 mL of a 0.1N hydrochloric acid aqueous solution with a known titer was taken as a standard solution and added, and the mixture was titrated again with 0.1N sodium hydroxide benzyl alcohol solution until the color change point. The titer (f) was then calculated using the following formula (4). Titer (f) = Titer of 0.1N hydrochloric acid solution × Amount of 0.1N hydrochloric acid solution collected (μL) / Titration volume of 0.1N sodium hydroxide benzyl alcohol solution (μL) ... (4)

[0093] (Measurement of the number of foreign particles in the resin) 10 kg of polyester resin sample was crystallized and dried in a hot air dryer at 160°C for 4 hours to reduce the moisture content to 100 ppm or less. Then, using a 20 mm diameter single-screw extruder, the resin was melt-extruded at a resin temperature of 285°C and an extrusion speed of 8 kg / hour to obtain a film with a thickness of 50 μm and a width of 100 mm from a 150 mm T-die. Next, after confirming the film thickness range by focusing on the front and back surfaces of the film, an image processing device (Opical Control Systems, FS-5 FILM SCAN) was used to capture images by focusing and scanning from the front to the back surface in grayscale image accumulation input mode. The maximum value of the straight-line distance between two points on the periphery of particles recognized by the image processing device was defined as the maximum diameter, and the number of particles with a maximum diameter of 25 μm or more was counted. This operation was repeated three times in different fields of view, and the average of these counts was calculated as 1 m². 2 This was converted to a per-film area ratio.

[0094] (Volume resistivity (ρV)) 23 g of polyester resin sample was placed in a branched test tube with an inner diameter of 20 mm and a length of 180 mm, and the inside of the tube was thoroughly purged with nitrogen. Then, it was immersed in an oil bath at 160°C and vacuum-dried for 4 hours with the pressure inside the tube reduced to less than 1 Torr using a vacuum pump. Next, the oil bath temperature was raised to 295°C to melt the resin sample, and then mixed air bubbles were removed by repeatedly restoring and depressurizing with nitrogen. In this molten material, an area of ​​1 cm² was added. 2 Two stainless steel electrode plates were inserted parallel to each other with a 5mm gap between them (the non-opposing back surfaces were covered with an insulator). After the temperature stabilized, a DC voltage of 100V was applied between the electrodes using a resistance meter (Hewlett-Packard "MODEL HP4339B"), and the volume resistivity (Ω·cm) was determined from the resulting resistance.

[0095] <Manufacturing of polyester resin> A continuous polyester resin manufacturing apparatus was used, comprising: a slurry preparation tank equipped with a stirrer, ethylene glycol charging piping, and terephthalic acid charging piping; piping for transferring the slurry and esterification reaction products to each esterification reaction tank; fully mixed first and second stage esterification reaction tanks equipped with a stirrer, separation column, raw material receiving port, catalyst charging piping, and reaction product transfer piping; piping for transferring the esterification reaction products (oligomers) to a melt polycondensation reaction tank; a fully mixed first stage melt polycondensation reaction tank equipped with a stirrer, separation column, oligomer receiving port, and catalyst charging piping; plug-flow type second and third stage melt polycondensation reaction tanks equipped with a stirrer, separation column, polymer receiving port, and polymer extraction port; and a pelletizing device that extracts the polymer in strand form from a die plate via a gear pump through an extraction port and cuts the strands under water cooling.

[0096] [Example 1] Using the continuous polyester resin manufacturing apparatus described above, an esterification reaction was carried out using a dicarboxylic acid and synthesis gas-derived ethylene glycol containing an acetal compound as a diol composition in the amounts shown in Table 2. Further, a melt polycondensation reaction was performed, and the resulting molten polyester resin was extracted from the die plate in strand form and cut to produce polyester resin. Table 2 shows the content of diethylene glycol and compounds (1) to (5) in the diol compositions used above, as well as the various physical properties of the resulting polyester resin.

[0097] A slurry was prepared in a slurry preparation tank by supplying an ethylene glycol solution of ethyl acid phosphate (concentration 0.3% by mass) at a concentration of 0.56 mol / t of phosphorus atoms relative to the polyester resin to be produced, along with terephthalic acid and ethylene glycol, in a mass ratio of terephthalic acid:ethylene glycol = 865:485. In the first stage esterification reaction tank, which was maintained under a nitrogen atmosphere at a temperature of 270°C and a pressure of 10 kPaG, the slurry prepared in the slurry preparation tank was continuously charged at a rate of 105 parts by mass / hour so that the average residence time of the reactants was 2.5 hours. The esterification reaction was carried out while the water generated from the separation column was distilled off, and the reactants were continuously transferred to the second esterification reaction tank.

[0098] In the second-stage esterification reactor, the esterification reaction was carried out at a temperature of 265°C, a pressure of 0 kPaG, and an average residence time of 1.0 hour. The product was then continuously transferred through a transfer pipe to a fully mixed first-stage melt polycondensation reactor. During the transfer, an ethylene glycol solution of magnesium acetate tetrahydrate (concentration 6.4% by mass) was added to the esterification reaction product at a concentration of 1.06 mol / t of magnesium atoms relative to the resulting polyester resin. Subsequently, an ethylene glycol solution of antimony trioxide (concentration 2.0% by mass) was added to the resulting polyester resin at a concentration of 1.96 mol / t of antimony atoms, both of which were continuously added.

[0099] In the first stage molten polycondensation reactor, the reaction was carried out at a temperature of 266°C, an absolute pressure of 3.25 kPa, and an average residence time of 0.85 hours. The resulting mixture was then continuously transferred to the second stage molten polycondensation reactor via a transfer pipe. In the second stage melt polycondensation reactor, a melt polycondensation reaction was carried out at a temperature of 270°C, an absolute pressure of 0.31 kPa, and a residence time of 0.90 hours, and the resulting mixture was continuously transferred to the third stage melt polycondensation reactor via a transfer pipe.

[0100] In the third stage melt polycondensation reaction vessel, a melt polycondensation reaction was carried out at a temperature of 272°C, an absolute pressure of 0.26 kPa, and an average residence time of 0.66 hours to obtain polyester resin. The polyester resin was extruded from the die in strand form, cooled and solidified, and then cut with a cutter to form pellets.

[0101] [Comparative Example 1] Polyester resin pellets were obtained in the same manner as in Example 1, except that a petroleum-derived ethylene glycol containing an acetal compound in the amount shown in Table 2 was used as the diol composition.

[0102] [Comparative Example 2] Polyester resin pellets were obtained in the same manner as in Example 1, except that a petroleum-derived ethylene glycol containing an acetal compound in the amount shown in Table 2 was used as the diol composition.

[0103] [Table 2]

[0104] In the examples, the number of granular particles (foreign matter) contained in the obtained polyester resin was suppressed. Furthermore, the polyester resin obtained in the examples showed a tendency for a decrease in the b-value.

Claims

1. A polyester resin made from a diol composition containing ethylene glycol as the main component, A polyester resin wherein the diol composition satisfies the following condition (I). 0.01≦q≦20.0 (I) However, q = c + e c = (mass concentration of the compound represented by formula (3) below / 134.13) / (mass concentration of ethylene glycol / 62.07) (mol ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) 【Chemistry 1】

2. The polyester resin according to claim 1, wherein the diol composition satisfies the following condition (II). 0.01≦r≦50.0 (II) However, r = a + c + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) c = (mass concentration of the compound represented by formula (3) below / 134.13) / (mass concentration of ethylene glycol / 62.07) (mol ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) 【Chemistry 2】

3. The polyester resin according to claim 1, wherein the diol composition satisfies the following condition (III). 0.01≦s≦70.0 (III) However, s=a+b+c+d+e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) b = (mass concentration of the compound represented by formula (2) below / 148.16) / (mass concentration of ethylene glycol / 62.07) (mol ppm) c = (mass concentration of the compound represented by formula (3) below / 134.13) / (mass concentration of ethylene glycol / 62.07) (mol ppm) d = (mass concentration of the compound represented by formula (4) below / 120.10) / (mass concentration of ethylene glycol / 62.07) (mol ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) 【Transformation 3】

4. The polyester resin according to claim 1, wherein the content (a) of the compound represented by the following formula (1) in the diol composition is 30 mol ppm or less. However, a = (mass concentration of the compound represented by formula (1) below / 148.16) / (mass concentration of ethylene glycol / 62.07) (mol ppm) 【Chemistry 4】

5. The polyester resin according to claim 1, wherein the content (e) of the compound represented by the following formula (5) in the diol composition is 15 mol ppm or less. However, e = (mass concentration of the compound represented by formula (5) below / 166.17) / (mass concentration of ethylene glycol / 62.07) (mol ppm) 【Transformation 5】

6. The polyester resin according to claim 1, wherein the diol composition contains diethylene glycol, and the content of diethylene glycol per 100 moles of ethylene glycol is 150 moles ppm or less.

7. The polyester resin according to claim 1, wherein the specific gravity of the diol composition is 1.1120 to 1.1140.

8. The volume resistivity (ρV) is 10 × 10 ７ The polyester resin according to claim 1, wherein the density is Ω·cm or less.

9. When a film with a thickness of 50 μm is made, 1 m of film ２ The polyester resin according to claim 1, wherein the number of granular particles with a particle size of 25 μm or more present per unit area is 1700 or less.

10. The polyester resin according to claim 1, for use in manufacturing polyester film.

11. A polyester film formed from the polyester resin according to any one of claims 1 to 10.

12. The polyester film according to claim 11, which is for use as an optical component.

13. A method for producing a polyester resin using a diol composition mainly composed of a dicarboxylic acid component and ethylene glycol as raw materials, A method for producing a polyester resin, wherein the diol composition satisfies the following condition (I). 0.01≦q≦20.0 (I) However, q = c + e c = (mass concentration of the compound represented by formula (3) below / 134.13) / (mass concentration of ethylene glycol / 62.07) (mol ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) 【Transformation 6】

14. A method for producing a polyester resin according to claim 13, wherein the diol composition satisfies the following condition (II). 0.01≦r≦50.0 (II) However, r = a + c + e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) c = (mass concentration of the compound represented by formula (3) below / 134.13) / (mass concentration of ethylene glycol / 62.07) (mol ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) 【Transformation 7】

15. A method for producing a polyester resin according to claim 13, wherein the diol composition satisfies the following condition (III). 0.01≦s≦70.0 (III) However, s=a+b+c+d+e a = (Mass concentration of the compound represented by formula (1) below / 148.16) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) b = (mass concentration of the compound represented by formula (2) below / 148.16) / (mass concentration of ethylene glycol / 62.07) (mol ppm) c = (mass concentration of the compound represented by formula (3) below / 134.13) / (mass concentration of ethylene glycol / 62.07) (mol ppm) d = (mass concentration of the compound represented by formula (4) below / 120.10) / (mass concentration of ethylene glycol / 62.07) (mol ppm) e = (Mass concentration of the compound represented by formula (5) below / 166.17) / (Mass concentration of ethylene glycol / 62.07) (mol ppm) 【Transformation 8】

16. The method for producing a polyester resin according to claim 13, wherein the polyester resin is produced by at least an esterification step or a transesterification step and a polycondensation step.

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