Polyester resin composition and polyester film made therefrom

Abstract

This invention provides a polyester resin composition derived from chemical recycling that exhibits excellent transparency, low levels of minute foreign matter, and heat resistance, possesses an intrinsic viscosity suitable for film molding, and has excellent electrostatic application properties for film, thereby significantly increasing film yield. [Solution] A polyester resin composition containing chemically recycled polyethylene terephthalate, wherein the following (1) to (5) are within the specified range. (1) Intrinsic viscosity of polyester resin composition, (2) The amount of antimony element contained in the polyester resin composition, (3) The molar ratio of metal elements and phosphorus elements contained in the polyester resin composition, (4) The isophthalic acid content in the chemically recycled polyethylene terephthalate, and (5) Content of coarse foreign matter with an equivalent circular diameter of 1 μm or more in the chemically recycled polyethylene terephthalate.

Description

[Technical Field]

[0001] This invention relates to a polyester resin composition derived from chemical recycling and a polyester film thereof. [Background technology]

[0002] Polyesters possess excellent mechanical, thermal, chemical, electrical, and moldability properties, making them suitable for a wide range of applications. Among polyesters, polyethylene terephthalate (PET) is particularly popular due to its superior transparency and processability, making it widely used in applications requiring high quality, such as optical films and release films. However, as the range of applications expands, the required quality also increases, creating a demand for resin compositions that suppress the causes of film defects, such as metallic impurities.

[0003] Furthermore, when forming polyester resin into film, electrostatic casting is often employed, in which a high voltage is applied to the upper surface of an unsolidified sheet-like material, causing the sheet-like material to adhere tightly to a rotating cooling drum. However, when the speed of the rotating cooling drum is increased to increase the film formation speed in electrostatic casting, the adhesion force between the sheet-like material and the rotating cooling drum decreases, resulting in reduced uniformity of film thickness and transparency, as well as defects on the film surface due to uneven voltage application.

[0004] Furthermore, since process films such as release films are discarded after use, there has been a growing demand in recent years for reducing their environmental impact.

[0005] One way to reduce environmental impact is through thermal recycling, which involves burning discarded polyester resin to obtain thermal energy. However, thermal recycling generates carbon dioxide and results in the loss of polyester raw materials, meaning that new petroleum raw materials must be used to reproduce polyester.

[0006] To address these challenges, Patent Document 1 discloses technology related to film recovered from PET bottles. Patent Document 2 discloses recycled polyester resin using used polyester products. Patent Document 3 discloses polyester resin in which impurities that are difficult to remove by filtration are reduced by using an aluminum catalyst. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2017-7175 [Patent Document 2] Japanese Patent Publication No. 2022-40153 [Patent Document 3] Japanese Patent Publication No. 2024-28087 [Overview of the project] [Problems that the invention aims to solve]

[0008] Patent Document 1 discloses a laminated film made from polyester resin recycled from PET bottles. However, repeated material recycling of polyester resin by remelting it leads to thermal decomposition, hydrolysis, and oxidative decomposition of the polyester resin, resulting in a decline in quality such as discoloration, generation of foreign matter, and a decrease in mechanical strength due to a decrease in molecular weight.

[0009] Patent Document 2 discloses a method for obtaining chemically recycled polyester resin by depolymerizing used polyester products using ethylene glycol and then polycondensing them. However, because it is difficult to avoid the inclusion of isophthalic components and other copolymer components, there are problems such as a decrease in product yield and a decrease in mechanical strength.

[0010] Patent Document 3 discloses obtaining a chemically recycled polyester resin by adding an aluminum catalyst and a phosphorus catalyst to chemically recycled raw materials. However, because alkali metals and alkaline earth metals are not added, the film tends to adhere to the electrostatically charged casting drum during melt film formation, resulting in poor film yield.

[0011] The object of the present invention is to provide a polyester resin composition and a polyester film that utilize a chemically recycled polyester resin composition, exhibiting excellent transparency, low levels of fine foreign matter, heat resistance, an intrinsic viscosity suitable for film molding, excellent electrostatic application properties, and significantly increased film yield. [Means for solving the problem]

[0012] As a result of diligent research to solve the above problems, the present invention has the following configuration. The object of the present invention is achieved by the following means. [Item 1] A polyester resin composition comprising chemically recycled polyethylene terephthalate and characterized by satisfying the following (1) to (5). (1) The intrinsic viscosity of the polyester resin composition is 0.60 dL / g or more and 0.70 dL / g or less. (2) The antimony element content of the polyester resin composition is 50 ppm by weight or more and 120 ppm by weight or less, relative to the total weight of the polyester resin composition. (3) The molar ratio of metal elements to phosphorus elements contained in the polyester resin composition (M / P = (M1 + M2 / 2) / P) satisfies the following formula 1.5 ≤ (M1 + M2 / 2) / P ≤ 4.0 (M1: Content of divalent metal elements selected from Mg, Mn, and Ca (mol / t)) M2: Content of monovalent metal elements selected from Li, Na, and K (mol / t) P: Phosphorus element content (mol / t)) (4) When the isophthalic acid component content in the chemically recycled polyethylene terephthalate is measured 10 times, the isophthalic acid component content is 50 ppm by weight or more and 10,000 ppm by weight or less, and the standard deviation of the measured values is 1000 ppm by weight or less (5) The content of coarse foreign matters having a circular equivalent diameter of 1 μm or more in the chemically recycled polyethylene terephthalate is 800 pieces / 0.1 mm or less [Item 2] The polyester resin composition according to [Item 1], characterized in that the b value of the color tone in the color difference meter is 10 or less. [Item 3] The polyester resin composition according to [Item 1], wherein the content of magnesium element is 30 ppm by weight or more and 80 ppm by weight or less based on the total weight of the polyester resin composition. [Item 4] The polyester resin composition according to [Item 1], wherein the content of phosphorus element is 10 ppm by weight or more and 90 ppm by weight or less based on the total weight of the polyester resin composition. [Item 5] The polyester resin composition according to [Item 1], containing one or more kinds of particles selected from aggregated silica, colloidal silica, alumina, calcium carbonate, and crosslinked polystyrene. [Item 6] A polyester film using the polyester resin composition according to [Item 1] to [Item 5]. [Advantages of the Invention]

[0013] The present invention applies a polyester resin composition derived from chemical recycling, has few foreign matters, is excellent in transparency, heat resistance, has an intrinsic viscosity suitable for film molding, is excellent in film electrostatic charging property, and significantly increases the film yield. Provided are a polyester resin composition and a polyester film. [Embodiments for Carrying Out the Invention]

[0014] The present invention will be described in detail below. In this specification, "weight", "weight %", "weight ppm", and "parts by weight" are synonymous with "mass", "mass %", "mass ppm", and "parts by mass", respectively. "Element" may also be used synonymously with "atom".

[0015] The polyester resin composition of the present invention refers to a polyester resin composition obtained by polycondensing a dicarboxylic acid component and a diol component. Examples of the dicarboxylic acid component include terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, 4,4'-diphenyldicarboxylic acid, 5-sodium sulfoisophthalic acid, oxalic acid, succinic acid, adipic acid, sebacic acid, malonic acid, dimer acid, and the like. A more preferred embodiment of the dicarboxylic acid of the present invention is terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, or an alkyl ester thereof, in that a polyester composition having a high melting point and easy to process into films, fibers, etc. can be obtained. Particularly, from the viewpoints of polymerization property and mechanical properties, terephthalic acid is most preferred.

[0016] As the diol component, various diols can be used. For example, aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, butanediol, and neopentyl glycol, alicyclic diols such as cyclohexanedimethanol and cyclohexanedietanol, and aromatic cyclic diols such as bis-phenol A, bis-phenol S, styrene glycol, 9,9-bis-(4-(2-hydroxyethoxy)phenyl)fluorene, and 9,9'-bis-(4-hydroxyphenyl)fluorene can be exemplified. Among these, ethylene glycol is particularly preferred from the viewpoint of mechanical properties.

[0017] Also, within a range not impairing the effects of the present invention, those copolymerized using one or more of the above dicarboxylic acid component, diol component, and further hydroxycarboxylic acid, etc. may be used.

[0018] The polyester resin composition of the present invention needs to contain chemically recycled polyethylene terephthalate.

[0019] Chemically recycled polyethylene terephthalate is a polyester resin composition obtained by depolymerizing used polyester products such as PET bottles, polyester films, clothing, and containers, as well as waste products from manufacturing before product extraction, products that were not shipped to market as B-grade products, selvage portions held during film stretching, and slitting scraps. These materials are then purified and repolymerized. When polyester film is used as the raw material for recycling, it is preferable to use biaxially oriented polyester film for process release. Furthermore, the main component is preferably polyethylene terephthalate. These raw polyester resins may be derived from petroleum, biomass, or mechanical recycling. They may also be mixtures of these polyester resins.

[0020] Depolymerization is a process in which polyester is depolymerized with a diol compound to obtain a depolymerized solution. The diol compound used is not particularly limited, but ethylene glycol, propylene glycol, and butylene glycol are preferred, and ethylene glycol is more preferred in order to improve the yield of the resulting bis-(2-hydroxyethyl) terephthalate.

[0021] Furthermore, depolymerization can be carried out efficiently by using a catalyst. The catalyst used is not limited, but examples include metal hydroxide salts such as sodium hydroxide, potassium hydroxide, and magnesium hydroxide; metal acetate salts such as magnesium acetate, manganese acetate, and calcium acetate; and organic hydroxide salts such as tetraethylammonium hydroxide, tetrabutylammonium hydroxide, and tetrabutylphosphonium hydroxide. Among these, metal hydroxide salts and metal acetate salts are preferred in terms of the quality of the resulting polymer.

[0022] The resulting reaction product can be purified by methods such as filtration, decolorization, distillation, and crystallization of the solid components, thereby improving the purity of bis-(2-hydroxyethyl) terephthalate.

[0023] The present invention relates to a method for producing chemically recycled polyester, characterized by condensation polymerization of bis-(2-hydroxyethyl) terephthalate obtained by chemical recycling.

[0024] The bis-(2-hydroxyethyl) terephthalate that has undergone chemical recycling may contain, in addition to bis-(2-hydroxyethyl) terephthalate, bis-(2-hydroxyethyl) isophthalate, dimers or larger polymers of the carboxylic acid diester, carboxylic acid monoesters such as mono-(2-hydroxyethyl) terephthalate, dicarboxylic acids such as terephthalic acid and isophthalic acid, diols such as ethylene glycol, water, and the like.

[0025] Bis-(2-hydroxyethyl) terephthalate that has undergone chemical recycling often contains isophthalic acid components. In the present invention, the isophthalic acid content (average value of 10 measurements) must be between 50 ppm by weight and 10,000 ppm by weight, and more preferably between 50 ppm by weight and 5,000 ppm by weight. If the isophthalic acid content exceeds 10,000 ppm by weight, it is undesirable because it impairs thermal properties such as melting point and glass transition temperature compared to a polyester resin composition composed solely of terephthalic acid components.

[0026] For example, since PET bottles often contain about 10,000 ppm by weight of isophthalic acid in the polyester resin, the proportion of bis-(2-hydroxyethyl) terephthalate used in chemical recycling is adjusted so that the isophthalic acid content falls within the above range.

[0027] In the polyester resin composition of the present invention, the standard deviation of the measured values ​​when the isophthalic acid content is measured 10 times must be 1000 ppm by weight or less. If this standard deviation is greater than 1000 ppm by weight, unevenness in thermal properties may occur, and surface defects may occur in the film during stretching.

[0028] The intrinsic viscosity of the polyester resin composition of the present invention must be 0.60 dL / g or higher. If it is lower, the mechanical properties during film molding may be unsuitable. Furthermore, if the intrinsic viscosity is 0.70 dL / g or higher, it may reduce the temperature rise due to shear heat generation during melt extrusion in film molding, suppress the regeneration of cyclic trimers during resin melting, and may also lead to deterioration of the mechanical properties during film molding due to thermal degradation of the resin.

[0029] The polyester resin composition of the present invention must contain an antimony element in a range of 50 ppm by weight or more and 120 ppm by weight or less. If the antimony element content is less than 50 ppm by weight, polymerization activity will be insufficient, and the polyester resin composition may not reach the target intrinsic viscosity. Furthermore, if the antimony element content exceeds 120 ppm by weight, the amount of metallic antimony in the polyester resin composition will be high, which is undesirable as it will become a foreign substance during film processing. From the viewpoint of suppressing the deterioration of solution haze and suppressing metallic antimony in the polyester resin composition, the antimony element content is preferably in the range of 50 ppm by weight to 120 ppm by weight, and more preferably in the range of 50 ppm by weight to 100 ppm by weight.

[0030] The polyester resin composition of the present invention contains a phosphorus compound. The phosphorus content is preferably 5 ppm to 90 ppm by weight, and more preferably 5 ppm to 40 ppm by weight, relative to the total weight of the polyester resin composition. A phosphorus content exceeding 90 ppm by weight is undesirable because it increases the reaction time required to reach the predetermined intrinsic viscosity, increases the amount of impurities, and worsens the solution haze of the polyester resin composition. A phosphorus content of less than 5 ppm by weight is undesirable because it worsens the heat resistance.

[0031] The polyester resin composition of the present invention must satisfy the following formula for the molar ratio of the contained metal element to the phosphorus element (M / P = (M1 + M2 / 2) / P). 1.5 ≤ (M1 + M2 / 2) / P ≤ 4.0

[0032] Here, M1 is the content of a divalent metal element selected from Mg and Mn (mol / t), M2 is the content of a monovalent metal element selected from Li, Na, and K (mol / t), and P is the content of phosphorus (mol / t). If M / P exceeds 4.0, the heat resistance deteriorates and it becomes unsuitable; preferably it is 2.5 or less. Also, if M / P falls below 1.5, the reduction in gelation rate is insufficient.

[0033] The amount of carboxyl-terminal groups in the polyester resin composition of the present invention is preferably greater than 15 eq / t and less than or equal to 50 eq / t. When it is 15 eq / t or less, the heat resistance tends to be very good, but intramolecular interactions are low and the uniformity of molecular orientation decreases, so thickness variations are likely to occur during film molding. In addition, in the width direction, the uniformity of molecular orientation tends to decrease between the center and both ends in the width direction, and if the film is thin, it may be more prone to breakage. Furthermore, when it exceeds 50 eq / t, the molecular mobility of the polyester resin tends to increase, so the heat resistance decreases and the flatness tends to deteriorate due to the occurrence of heat wrinkles when heated during film formation. Moreover, the molecular chains of the polyester resin are short, which tends to cause thickness variations during film manufacturing.

[0034] The diethylene glycol content of the polyester resin composition of the present invention is preferably 1.2% by weight or less, relative to the weight of the film. More preferably, it is 1.0% by weight or less, and even more preferably 0.9% by weight or less. By keeping the content within this range, a polyester film with good heat resistance and excellent mechanical strength can be obtained.

[0035] To stabilize the diethylene glycol in the polyester resin composition of the present invention, it is also preferable to minimize the generation of diethylene glycol when producing bis-(2-hydroxyethyl) terephthalate through chemical recycling.

[0036] The polyester resin composition of the present invention preferably has a b-value of 10.0 or less, as measured by a colorimeter. More preferably, it is 9.0 or less. When the b-value is 10.0 or less, the amount of foreign matter in the chemically recycled bis-(2-hydroxyethyl) terephthalate is low, and the thermal history of the polyester resin composition is low, making it possible to produce a polyester film with excellent mechanical strength.

[0037] The polyester resin composition of the present invention may contain particles.

[0038] Examples of particles to be included in the polyester resin composition of the present invention include aggregated silica, colloidal silica, alumina, barium sulfate, barium carbonate, magnesium oxide, magnesium sulfate, magnesium carbonate, zinc oxide, zinc sulfide, zinc carbonate, titanium dioxide, cerium oxide, zirconium oxide, iron oxide, kaolin, talc, mica, carbon black, silicon, crosslinked polystyrene, crosslinked silicon, crosslinked acrylic, crosslinked styrene-acrylic, crosslinked polyester, polyimide, and melamine, but the type of particle is not particularly limited. Among these, aggregated silica, colloidal silica, alumina, calcium carbonate, and crosslinked polystyrene are preferred from the viewpoint of economy, thermal stability, and particle dispersibility.

[0039] The method for incorporating particles into the polyester resin composition of the present invention is not particularly limited, but from the viewpoint of improving particle dispersibility, it is preferable to incorporate them into the polyester resin composition by adding them during the polycondensation reaction of the polyester resin composition or by kneading them with the polyester resin composition after the polycondensation reaction using a twin-screw kneading extruder or the like. Furthermore, the number of particle species to be incorporated into the polyester resin composition of the present invention is not particularly limited as long as it does not impair the effects of the present invention, and one or more types of particles can be incorporated.

[0040] The particles incorporated into the polyester resin composition of the present invention may be in the form of either a powder or a slurry, but it is preferable to add them as a slurry from the viewpoint of dispersibility. The slurry may be either a water slurry or a slurry of the diol component of the polyester composition, but from the viewpoint of particle dispersibility of the polyester resin composition, it is preferable that it be the same as the diol component of the polyester.

[0041] The polyester resin composition of the present invention, when a polyester resin composition treated under the following processing conditions is observed at 1000x magnification with a scanning electron microscope (SEM), contains 800 coarse foreign matter particles with an equivalent circle diameter of 1 μm or more per 0.1 mm. 2 The following is required: Preferably 700 pieces / 0.1 mm 2 More preferably, 500 pieces / 0.1 mm 2 The following is the result: 800 coarse foreign objects per 0.1 mm 2 If this value is exceeded, the resulting polyester resin composition will produce a film with many defects.

[0042] Processing conditions: Using a PR300 plasma reactor manufactured by Yamato Scientific Co., Ltd., the polyethylene terephthalate resin composition is removed by low-temperature plasma ashing treatment for 5 minutes under vacuum conditions of -0.1 MPa or less, with an air flow rate of 60 ml / min and an output of 100 W, exposing coarse foreign matter. The specific method for measuring the content of coarse foreign matter will be explained in the examples.

[0043] The method for producing the polyester resin composition of the present invention is described below in detail. In the method for producing the polyester resin composition, it is preferable to add chemically recycled bis-(2-hydroxyethyl) terephthalate to a polymerization tank, then raise the temperature of the polymerization tank to stabilize it in a heated molten state. Subsequently, it is preferable to add additives such as antimony element, magnesium element, and phosphorus element, which are polycondensation catalysts, and then increase the temperature inside the apparatus and perform condensation polymerization by reducing the pressure.

[0044] Methods for adding chemically recycled bis-(2-hydroxyethyl) terephthalate to the polymerization tank include, but are not limited to, methods of supplying bis-(2-hydroxyethyl) terephthalate in liquid form after heating and melting, and methods of supplying bis-(2-hydroxyethyl) terephthalate in flake or briquette form.

[0045] While batch polymerization and continuous polymerization are well-known methods for producing polyester compositions, continuous polymerization is preferred because it involves less thermal history and the quality of the polyester resin composition is more stable.

[0046] When producing the polyester resin composition of the present invention in a continuous polymerization facility, the number of reaction vessels is not particularly limited, but it is preferable to use three or more vessels from the viewpoint of reaction efficiency.

[0047] The internal temperature of the apparatus is preferably 120 to 290°C, and more preferably 140 to 280°C. The pressure is preferably between 0.01 kPa and 300 kPa, and more preferably 0.1 kPa to 250 kPa.

[0048] Furthermore, when adding copolymer components or when bis-(2-hydroxyethyl) terephthalate that has undergone chemical recycling contains dicarboxylic acid components, it is preferable to add an esterification step before the polycondensation step.

[0049] Regarding the copolymerization component, polycarboxylic acids are preferred, and terephthalic acid is particularly preferred.

[0050] After the polymerization reaction is complete, the resulting molten polyester resin can be extruded in strand form from a nozzle, cooled, and then pelletized using a cutter to produce a polyester resin composition.

[0051] When producing the polyethylene terephthalate resin composition of the present invention using a continuous polymerization apparatus, it is necessary to include a step of removing foreign matter during the polymerization reaction.

[0052] The process for removing foreign matter is not particularly limited; processes such as passing the material through a filtration filter or through a centrifugal separator can be employed.

[0053] Regarding the dimensions of the foreign matter to be removed, it is preferable that the smallest equivalent circular diameter of the removed foreign matter is 5 μm or less, and more preferably 1 μm or less.

[0054] The process of removing foreign matter during the production of the polyester resin composition of the present invention may include one or more steps, and it is not problematic to include two or more steps. Furthermore, each step may target foreign matter of a different equivalent circle diameter, and as long as the minimum equivalent circle diameter of foreign matter removed in one of the multiple foreign matter removal steps is 5 μm or less, the foreign matter removal capacity of the other foreign matter removal steps is not particularly limited.

[0055] Furthermore, when producing the polyester resin composition of the present invention by batch polymerization, it is preferable to use two or more polymerization tanks, and it is preferable to include a step to remove foreign matter when transferring the liquid between polymerization tanks.

[0056] The obtained polyester resin composition is preferably pre-crystallized before the drying process. Pre-crystallization can be carried out by methods such as applying mechanical impact to the polyester resin composition to subject it to shear treatment, or by applying heat treatment under hot air circulation.

[0057] In order to obtain a high molecular weight polyester resin composition, solid-phase polymerization may be performed on the polyester resin composition of the present invention. The apparatus and method of solid-phase polymerization are not particularly limited, but it is carried out by heating the polyester composition under an inert gas atmosphere or under reduced pressure at a temperature below the melting point of the polyester resin composition. The inert gas can be any gas that is inert to the polyester resin composition, such as nitrogen, helium, or carbon dioxide, but nitrogen is preferably used for economic reasons. Furthermore, under reduced pressure conditions, it is advantageous to create a higher vacuum so as to shorten the time required for the solid-phase polymerization reaction, and it is specifically preferable to maintain a vacuum of 110 Pa or less. [Examples]

[0058] The present invention will be described in more detail below with reference to the following examples. The physical properties in the examples were measured by the following method.

[0059] (1) Method for measuring isophthalic acid in bis-(2-hydroxyethyl) terephthalate and polyester resin compositions 0.2 g of bis-(2-hydroxyethyl) terephthalate or polyester resin composition was weighed and dissolved at 260°C in 15 mL of 1 M sodium methylate solution and 15 mL of methyl acetate, then cooled. After cooling, aqueous acetic acid solution was added to the solution to neutralize it, and salting out was performed by adding saturated saline solution. The solution was then extracted with chloroform, the upper aqueous layer was discarded, and the chloroform layer was separated using filter paper. The isophthalic acid content of the chloroform filtrate was measured 10 times by high-performance liquid chromatography, and the average value was taken as the isophthalic acid content, along with the standard deviation.

[0060] (2) Method for determining the purity of bis-(2-hydroxyethyl)terephthalate 20 mg of bis-(2-hydroxyethyl) terephthalate was used as a sample, dissolved in orthochlorophenol at 150°C for 30 minutes, and then cooled to room temperature. The sample was then analyzed using a high-performance liquid chromatography (HPL) system. The peak area was determined by integrating the detector's output power over time from the peak derived from bis-(2-hydroxyethyl) terephthalate in the resulting chart. A calibration curve created from the peak area measurements of three known sample components was then used to obtain the weight percentage.

[0061] (3) Intrinsic viscosity of polyester resin composition [η] (unit: dL / g) 0.1 g of the polyester resin composition was weighed to an accuracy of 0.001 g or less and dissolved by heating in 10 mL of o-chlorophenol (hereinafter referred to as OCP) at 100 °C for 30 minutes. The solution was cooled to room temperature, and 8 mL of the solution was placed in an Ostwald viscometer set up in a 25 °C water bath, and the time it took to pass through the mark was measured (A seconds). In addition, 8 mL of OCP alone was used and the time it took to pass through the mark was measured in the same manner in an Ostwald viscometer set up in a 25 °C water bath (B seconds). The intrinsic viscosity [η] was calculated using the formula [η] = -1 + [1 + 4 × K × {(A / B) - 1}]^0.5 / (2 × K × C), where K is 0.343 and C is the concentration of the sample solution (g / 100 mL).

[0062] (4) Elemental content in polyester resin composition (unit: ppm by weight) The content of phosphorus (atoms), magnesium (atoms), and antimony (atoms) was determined by forming sample pellets of the polyester resin composition into cylindrical shapes using a melt press, and measuring the fluorescence X-ray intensity using a fluorescence X-ray analyzer (model: 3270) manufactured by Rigaku Denki Co., Ltd. The content was calculated from a calibration curve created from the measurement results of three sample levels with known content.

[0063] (5) Color b value of polyester resin composition Resin pellets of a polyester resin composition were filled into a cylindrical powder measurement cell, and the b-value was measured using the reflectance method with n=3 using a color difference meter (SM Color Meter SM-T) manufactured by Suga Test Instruments Co., Ltd. The arithmetic mean of the measured values ​​was used as the color tone b-value and as an evaluation index for color tone.

[0064] (6) Coarse foreign matter in the polyester resin composition (unit: pieces / 0.1 mm) 2 ) A polyethylene terephthalate resin composition was treated under the following conditions to obtain the measurement sample. Processing conditions: Using a plasma reactor PR300 manufactured by Yamato Scientific Co., Ltd., the polyethylene terephthalate resin composition is removed by low-temperature plasma ashing treatment for 5 minutes under vacuum conditions of -0.1 MPa or less, with an air flow rate of 60 ml / min and an output of 100 W, exposing coarse foreign matter.

[0065] The sample was observed using a scanning electron microscope (SEM), and the foreign object image was processed with an image analyzer. A magnification of 1000x was selected for the SEM. The observation area was changed to 0.1 mm. 2 The above measurements were performed, and for white objects, those with an equivalent circular diameter of 1 μm or more were considered foreign objects. The number of foreign objects was counted, and the value was calculated by dividing the count by the measured area.

[0066] (7) Amount of COOH-terminated groups in the polyester resin composition (unit: eq / t) The measurement was performed using Maurice's method (Reference: MJ Maurice, F. Huizinga, Anal. Chem. Acta, 22, 363 (1960)).

[0067] Specifically, 0.5 g of the polyester resin composition is weighed to an accuracy of 0.001 g or less. 50 ml of a solvent mixed with o-cresol / chloroform in a mass ratio of 7 / 3 is added to the sample, and the mixture is heated until the internal temperature reaches 90°C, then heated and stirred for 20 minutes to dissolve. The mixed solvent alone is also heated separately as a blank solution. The solution is cooled to room temperature, and titration is performed using a potentiometric titrator with a 1 / 50 N potassium hydroxide methanol solution. The blank solution of the mixed solvent alone is also titrated in the same manner.

[0068] The amount of COOH-terminal groups in the polyester resin composition was calculated using the following formula. COOH terminal group amount (eq / t)={(V1-V0)×N×f}×1000 / S

[0069] Here, V1 is the titration volume in the sample solution (mL), V0 is the titration volume in the blank solution (mL), N is the normality of the titrant (N), f is the titrant factor, and S is the mass of the polyester resin composition (g).

[0070] (8) Amount of diethylene glycol in the polyester resin composition (unit: weight %) 0.5 g of the polyester resin composition was weighed and dissolved at 260°C in 1.3 ml of monoethanolamine containing 0.4 wt / vol% 1,6-hexanediol. Methanol was added to the solution and it was cooled. Subsequently, it was neutralized with terephthalic acid, and the diethylene glycol content of the solution was measured by gas chromatography (Shimadzu Corporation, GC-2025).

[0071] (9) Gelation rate of polyester resin composition (unit: %) Resin pellets of a polyester resin composition were crushed using a freeze grinder (Sprex CertiPerp) and 0.5 g was weighed into a stainless steel beaker. After vacuum drying at 50°C for 2 hours using a vacuum dryer, the oxygen concentration was adjusted to 1% with a mixture of air and nitrogen. The 1% oxygen mixture was passed through the stainless steel beaker containing the weighed sample via a pipe, and the container was immersed in a 300°C oil bath. The mixture of air and nitrogen with an oxygen concentration of 1% was flowed at a flow rate of 0.5 L / min and the mixture was heat-treated for 6 hours. This was dissolved in 20 ml of OCP at 160°C for 1 hour and allowed to cool. This solution was filtered using a glass filter (Shibata Chemical Co., Ltd., 3GP40), and the glass filter was washed with dichloromethane. The glass filter was dried at 130°C for 2 hours. The weight of the OCP insoluble matter (gel) remaining in the filter was calculated from the increase in the weight of the glass filter before and after filtration. The weight fraction of the OCP insoluble matter relative to the weight of ethylene terephthalate was determined and expressed as the gelation rate (%). A gelation rate of 20.0% or less was considered good, a rate greater than 20.0% but 25.0% or less was considered acceptable, and a rate greater than 25.0% was considered unacceptable.

[0072] (10) Heat resistance of polyester resin composition (main chain fragmentation rate (%BB)) (unit: %) 5 g of the polyester resin composition was placed in a test tube, vacuum-dried at 160°C for 5 hours, and then melted in an oil bath at 290°C under a nitrogen flow of 300 mL / min for 6 hours. The main chain fragmentation rate (%) was calculated using the intrinsic viscosity [η]6hr of the molten material and the intrinsic viscosity [η]0hr before melting, using the formula: main chain fragmentation rate (%) = 0.27 × {[η]6hr^(-1.33) - [η]0hr^(-1.33)}. A value of 1.2% or less was considered a pass, and a value exceeding 1.2% was considered a fail.

[0073] (11) Film-forming properties of polyester films The polyester resin compositions obtained in the examples and comparative examples were supplied to an extruder, melt-extruded at 285°C, and cast onto a 20°C cast drum with electrostatic application to produce unstretched films. If the film could be produced without any problems, it was judged as "○"; if problems occurred with the extruder or cast drum, making film production difficult, it was judged as "×".

[0074] (Preparation of bis-(2-hydroxyethyl) terephthalate after chemical recycling) Bis-(2-hydroxyethyl) terephthalate A, bis-(2-hydroxyethyl) terephthalate B, bis-(2-hydroxyethyl) terephthalate C, and bis-(2-hydroxyethyl) terephthalate D were prepared by mixing (a) to (c) below so that the chemically recycled bis-(2-hydroxyethyl) terephthalate would have the physical properties shown in Table 1.

[0075] (a) Bis-(2-hydroxyethyl) terephthalate (isophthalic acid content: 5700 ppm by weight) produced by chemical recycling using PET bottles as the raw material.

[0076] (b) Bis-(2-hydroxyethyl) terephthalate (isophthalic acid content: 100 ppm by weight) produced by chemical recycling using PET film as the raw material.

[0077] (c) Bis-(2-hydroxyethyl) terephthalate (isophthalic acid content: 18,700 ppm by weight) produced through chemical recycling using PET bottles as the raw material.

[0078] (Example 1) In a 1L glass polymerization apparatus equipped with a stirrer, 133 parts by mass of bis-(2-hydroxyethyl) terephthalate A (equivalent to 100 parts by weight of polyester resin), dissolved at 230°C, were added. 0.0127 parts by weight of ethylene glycol solution of antimony trioxide, 0.0480 parts by weight of ethylene glycol solution of magnesium acetate, and 0.0006 parts by weight of ethylene glycol solution of potassium hydroxide were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0079] The properties of the obtained polyester resin composition are shown in Table 2. It contained antimony, magnesium, and phosphorus in the amounts listed in Table 2, with a COOH-terminal group content of 13 eq / t and a diethylene glycol content of 1.0% by weight. The b-value was 9.2, the gelation rate was 19.9%, the %BB was 1.0%, and the coarse foreign matter content was 470 particles / 0.1 mm. 2 It was within the acceptable range. The film-forming properties of the polyester film were evaluated favorably.

[0080] (Example 2) Into a 1 L glass polymerization apparatus equipped with a stirrer charged with 133 parts by mass of bis-(2-hydroxyethyl) terephthalate dissolved at 200 °C, an ethylene glycol solution of 0.0127 parts by weight of antimony trioxide, an ethylene glycol solution of 0.0480 parts by weight of magnesium acetate, and an ethylene glycol solution of 0.0006 parts by weight of potassium hydroxide were added. Further, an aqueous phosphoric acid solution was added in an amount of 0.0139 parts by weight as phosphoric acid. Subsequently, the inside of the polymerization apparatus was gradually depressurized, and at the same time, the temperature was gradually raised to 282 °C, and a polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. Thereafter, the polycondensation reaction vessel was returned to normal pressure with nitrogen gas, extruded in a strand form into cold water from a die, and pelletized into a columnar shape by an extrusion cutter to obtain a polyester resin composition.

[0081] The properties of the obtained polyester resin composition are shown in Table 2. It contained antimony element, magnesium element, and phosphorus element in the amounts described in Table 2, the amount of COOH end groups was 16 eq / t, and the amount of diethylene glycol was 0.4% by weight. The b value was 7.9, the gelation rate was 17.8%, %BB was 1.0%, and the amount of coarse foreign matter was 550 pieces / 0.1 mm. 2 and it was within the qualified range. The film-forming property evaluation of the polyester film was good.

[0082] (Example 3, Example 4, Comparative Example 1, Comparative Example 2) A polyester resin composition was obtained in the same manner as in Example 1 except that the addition amount of antimony trioxide was changed to the antimony element content described in Table 2. The physical properties of the polyester resin compositions obtained in Example 3 and Example 4 were all good or within the qualified range as described in Table 2. Also, in the evaluation of processing into a polyester film, the film-forming property was good. On the other hand, the polyester resin composition obtained in Comparative Example 1 failed in the evaluation of coarse foreign matter because of the high content of antimony element. The polyester resin composition obtained in Comparative Example 2 did not reach the target intrinsic viscosity because of the low content of antimony element. Therefore, in the film-forming property evaluation of the polyester film, the width of the extruded sheet was not constant, and it was difficult to form a film.

[0083] (Example 5, Comparative Example 3, Comparative Example 4) A polyester resin composition was obtained in the same manner as in Example 1, except that the amount of magnesium acetate added was changed to achieve the magnesium element content shown in Table 2. The physical properties of the polyester resin composition obtained in Example 4 showed an increased gelation rate, but all were good or within the acceptable range. In contrast, the polyester resin composition obtained in Comparative Example 3 failed the evaluation of the gelation rate due to its low M / P ratio. Furthermore, in the evaluation of the film-forming properties of the polyester film, the electrostatic casting properties were poor, making it difficult to create a film. The polyester resin composition obtained in Comparative Example 4 failed the evaluation of %BB due to its high M / P ratio.

[0084] (Examples 6, 7, 8, 5, and 6) A polyester resin composition was obtained in the same manner as in Example 1, except that the amount of phosphoric acid added was changed to achieve the magnesium content shown in Table 2. The physical properties of the polyester resin composition obtained in Example 5 showed an increased gelation rate, but all were good or within the acceptable range. The physical properties of the polyester resin compositions obtained in Examples 6 and 7 showed an increased heat resistance, but all were good or within the acceptable range. On the other hand, the polyester resin composition obtained in Comparative Example 5 failed the evaluation of the gelation rate due to its low M / P ratio. In addition, in the evaluation of the film-forming properties of the polyester film, the electrostatic casting properties were poor, making it difficult to create a film. The polyester resin composition obtained in Comparative Example 6 failed the evaluation of %BB due to its high M / P ratio.

[0085] (Example 9) In a 1L glass polymerization apparatus equipped with a stirrer, 133 parts by mass of bis-(2-hydroxyethyl) terephthalate A (equivalent to 100 parts by weight of polyester resin), dissolved at 230°C, were added. 0.0127 parts by weight of ethylene glycol solution of antimony trioxide, 0.0480 parts by weight of ethylene glycol solution of magnesium acetate, and 0.0006 parts by weight of ethylene glycol solution of potassium hydroxide were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.69 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0086] The physical properties of the polyester resin composition obtained in Example 9 were all good or within acceptable limits, as shown in Table 2. Furthermore, the film-forming properties were good when processed into a polyester film.

[0087] (Comparative Example 7) In a 1L glass polymerization apparatus equipped with a stirrer, 133 parts by mass of bis-(2-hydroxyethyl) terephthalate A (equivalent to 100 parts by weight of polyester resin), dissolved at 230°C, were added. 0.0127 parts by weight of ethylene glycol solution of antimony trioxide, 0.0480 parts by weight of ethylene glycol solution of magnesium acetate, and 0.0006 parts by weight of ethylene glycol solution of potassium hydroxide were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.56 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0088] The properties of the obtained polyester resin composition are shown in Table 2. Due to the low intrinsic viscosity of 0.56 dl / g, the width of the extruded sheet was inconsistent during the evaluation of the film-forming properties of the polyester film, making film production difficult.

[0089] (Comparative Example 8) In a 1L glass polymerization apparatus equipped with a stirrer, 133 parts by mass of bis-(2-hydroxyethyl) terephthalate A (equivalent to 100 parts by weight of polyester resin), dissolved at 230°C, were added. 0.0127 parts by weight of ethylene glycol solution of antimony trioxide, 0.0480 parts by weight of ethylene glycol solution of magnesium acetate, and 0.0006 parts by weight of ethylene glycol solution of potassium hydroxide were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.75 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0090] The properties of the obtained polyester resin composition are shown in Table 2. Due to its high intrinsic viscosity of 0.75 dl / g, the film-forming properties of the polyester film were difficult to evaluate because the molten polymer deteriorated due to shear heat generation in the extruder, resulting in frequent tearing during film formation.

[0091] (Example 10) In a 1L glass polymerization apparatus equipped with a stirrer, 133 parts by mass of bis-(2-hydroxyethyl) terephthalate B (equivalent to 100 parts by weight of polyester resin), dissolved at 230°C, were added. 0.0127 parts by weight of antimony trioxide in an ethylene glycol solution, 0.0480 parts by weight of magnesium acetate in an ethylene glycol solution, and 0.0006 parts by weight of potassium hydroxide in an ethylene glycol solution were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0092] As shown in Table 2, the physical properties of the polyester resin composition obtained in Example 10 were all good or within acceptable limits. Furthermore, in the evaluation after processing into polyester film, the film-forming properties were good.

[0093] (Example 11) In a 1L glass polymerization apparatus equipped with a stirrer, 3 parts by mass of bis-(2-hydroxyethyl) terephthalate C133 (equivalent to 100 parts by weight of polyester resin), dissolved at 230°C, were added. 0.0127 parts by weight of antimony trioxide in an ethylene glycol solution, 0.0480 parts by weight of magnesium acetate in an ethylene glycol solution, and 0.0006 parts by weight of potassium hydroxide in an ethylene glycol solution were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0094] The physical properties of the polyester resin composition obtained in Example 11 were all good or within acceptable limits, as shown in Table 2. Furthermore, the film-forming properties were good when processed into a polyester film.

[0095] (Comparative Example 9) In a 1L glass polymerization apparatus equipped with a stirrer, 0.0127 parts by weight of ethylene glycol solution of antimony trioxide, 0.0480 parts by weight of ethylene glycol solution of magnesium acetate, and 0.0006 parts by weight of ethylene glycol solution of potassium hydroxide were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0096] The properties of the obtained polyester resin composition are shown in Table 2. Due to the high concentration of isophthalic acid, it failed the %BB evaluation.

[0097] (Example 12) In a 1L glass polymerization apparatus equipped with a stirrer, 133 parts by mass of bis-(2-hydroxyethyl) terephthalate A (equivalent to 100 parts by weight of polyester resin), dissolved at 230°C, were added. 0.0084 parts by weight of antimony trioxide in an ethylene glycol solution, 0.0480 parts by weight of magnesium acetate in an ethylene glycol solution, and 0.01 parts by weight of lithium acetate in an ethylene glycol solution were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition.

[0098] The physical properties of the polyester resin composition obtained in Example 12 were all good or within acceptable limits, as shown in Table 2. Furthermore, the film-forming properties were good when processed into a polyester film.

[0099] (Example 13) In a 30L SUS polymerization apparatus equipped with a stirrer, 133 parts by mass of bis-(2-hydroxyethyl) terephthalate A dissolved at 230°C was charged. 0.0127 parts by weight of antimony trioxide in an ethylene glycol solution, 0.0480 parts by weight of magnesium acetate in an ethylene glycol solution, and 0.0006 parts by weight of potassium hydroxide in an ethylene glycol solution were added. Furthermore, 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. The pressure inside the polymerization apparatus was then gradually reduced, and simultaneously the temperature was gradually increased to 282°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. Afterward, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, and the mixture was discharged in strand form into cold water through a nozzle. The mixture was then pelletized into cylindrical shapes using an extruder to obtain the polyester resin composition. The physical properties of the polyester resin composition obtained in Example 13 were all good or within acceptable limits, as shown in Table 2. Furthermore, the film-forming properties were good in the evaluation of the polyester film.

[0100] (Comparative Example 10) A slurry consisting of 86 parts by weight of terephthalic acid and 37 parts by weight of ethylene glycol (1.15 times the molar amount of terephthalic acid) was gradually added to a 1 L glass polymerization apparatus equipped with a stirrer, and the esterification reaction was carried out while distilling off the water. After reacting with 105 parts by weight of the resulting esterified product (equivalent to 100 parts by weight of polyester resin), 0.0127 parts by weight of antimony trioxide in an ethylene glycol solution, 0.0480 parts by weight of magnesium acetate in an ethylene glycol solution, and 0.0006 parts by weight of potassium hydroxide in an ethylene glycol solution were added, and then 0.0139 parts by weight of an aqueous phosphoric acid solution was added as phosphoric acid. Subsequently, the pressure inside the polymerization apparatus was gradually reduced, and at the same time, the temperature was gradually increased to 282°C, and the polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.65 dl / g. After that, the polycondensation reaction vessel was returned to atmospheric pressure with nitrogen gas, the mixture was discharged in strand form into cold water from a nozzle, and pelletized into cylindrical shapes using an extruder cutter to obtain the polyester resin composition. The properties of the obtained polyester resin composition are shown in Table 2. Compared to Example 1, it failed the evaluation of coarse foreign matter.

[0101] [Table 1]

[0102] [Table 2-1]

[0103] [Table 2-2] [Industrial applicability]

[0104] The polyester resin composition obtained in this manner is suitable for use in films, and films made using this composition are useful for applications such as optical applications, agricultural materials, horticultural materials, fishing materials, civil engineering and construction materials, stationery, medical supplies, automotive parts, and electrical and electronic components, and are particularly suitable for release films used in processes where high quality is required.

Claims

1. A polyester resin composition containing chemically recycled polyethylene terephthalate and satisfying the following (1) to (5). (1) The intrinsic viscosity of the polyester resin composition is 0.60 dL / g or more and 0.70 dL / g or less. (2) The antimony element content is 50 ppm by weight or more and 120 ppm by weight or less relative to the total weight of the polyester resin composition. (3) The molar ratio of the amount of metal elements to phosphorus elements contained in the polyester resin composition (M / P = (M1 + M2 / 2) / P) satisfies the following formula 1.5≦(M1+M2 / 2) / P≦4.0 (M1: Content of divalent metal elements selected from Mg, Mn, and Ca (mol / t)) M2: Content of monovalent metal elements selected from Li, Na, and K (mol / t) P: phosphorus element content (mol / t)) (4) The isophthalic acid content in the chemically recycled polyethylene terephthalate is measured 10 times and is between 50 ppm by weight and 10,000 ppm by weight, and the standard deviation of the measured values ​​is 1,000 ppm by weight or less. (5) The amount of coarse foreign matter with an equivalent circle diameter of 1 μm or more in the chemically recycled polyethylene terephthalate is 800 pieces / 0.1 mm. ２ below

2. The polyester resin composition according to claim 1, characterized in that the color b value measured by a colorimeter is 10 or less.

3. The polyester resin composition according to claim 1, wherein the magnesium element content is 30 ppm by weight or more and 90 ppm by weight or less, relative to the total weight of the polyester resin composition.

4. The polyester resin composition according to claim 1, wherein the phosphorus element content is 10 ppm by weight or more and 90 ppm by weight or less, relative to the total weight of the polyester resin composition.

5. The polyester resin composition according to claim 1, comprising one or more particles selected from aggregated silica, colloidal silica, alumina, calcium carbonate, and cross-linked polystyrene.

6. A polyester film made using the polyester resin composition according to any one of claims 1 to 5.

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