Polyethylene terephthalate resin composition, polyester film, and method for producing polyethylene terephthalate resin composition

Abstract

To provide a polyethylene terephthalate resin composition which has less foreign matters, has good color tone, is excellent in transparency, and has heat resistance and good static-charge applicability, a polyester film formed of the polyethylene terephthalate resin composition, and a method for producing a polyethylene terephthalate resin composition.SOLUTION: A polyethylene terephthalate resin composition contains a p-toluene sulfonic acid component, and a quaternary phosphonium component, wherein the content of the p-toluene sulfonic acid component, the content of the quaternary phosphonium component, the content of a phosphorus element, and the total content of a manganese element and a potassium element, which are determined by liquid chromatography, with respect to the total weight of the polyethylene terephthalate resin composition are in the range described in the specifications, and when the polyethylene terephthalate resin composition treated under a treatment condition described in the specifications is observed by a scanning type electron microscope, the content of coarse foreign matters having an equivalent circle diameter of 1 μm or more is 450 pieces / 0.1 mm2 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyethylene terephthalate resin composition, a polyester film, and a method for producing a polyethylene terephthalate resin composition. [Background technology]

[0002] Polyesters have excellent mechanical properties, thermal properties, chemical resistance, electrical properties, and moldability, and are used in a variety of applications. Among polyesters, polyethylene terephthalate (hereinafter referred to as PET) in particular has excellent transparency and processability, and is therefore used in a variety of optical films, such as prism sheets for liquid crystal display components, light diffusion sheets, reflectors, base films for touch panels, anti-reflection base films, explosion-proof base films for displays, and PDP filter films. However, as the range of applications expands, the required quality also improves, and resin compositions that suppress causes of film defects such as metal foreign matter are desired.

[0003] Furthermore, when forming PET resin into a film, an electrostatic casting method is often used, in which a high voltage is applied to the top surface of an unsolidified sheet material to make it adhere to a rotating cooling drum. In this electrostatic casting method, if the speed of the rotating cooling drum is increased to increase the film production speed, the adhesion between the sheet material and the rotating cooling drum decreases, resulting in a decrease in the uniformity of film thickness and transparency, and defects on the film surface due to uneven voltage application.

[0004] To address these problems, for example, Patent Documents 1, 2 and 3 propose methods for producing polyester resin compositions in which a sulfonic acid compound or a phosphonium sulfonate compound is added, and further an alkali metal is added. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 15819 / 1983 [Patent Document 2] Special Publication No. 7-5765 [Patent Document 3] International Publication No. 2016 / 167084 Summary of the Invention [Problem to be solved by the invention]

[0006] However, simply adding a sulfonic acid compound or a phosphonium sulfonate compound to a polyester resin composition is insufficient to obtain electrostatic applicability for film formation. Furthermore, the addition of a sulfonic acid compound and an alkali metal leads to the generation of foreign matter, poor heat resistance of the polyester resin composition, and gelation. In other words, the above-mentioned conventional techniques are insufficient to simultaneously improve electrostatic applicability during film formation, reduce foreign matter derived from metal compounds, and suppress the generation of gelled matter by improving heat resistance. The object of the present invention is to provide a polyethylene terephthalate resin composition that contains little foreign matter, has good color tone, is excellent in transparency, and has heat resistance and good electrostatic applicability, as well as a method for producing the same. [Means for solving the problem]

[0007] As a result of extensive research to solve the above problems, the present invention has the following configuration. [1] A polyethylene terephthalate resin composition comprising a p-toluenesulfonic acid component and a quaternary phosphonium component, the content of the p-toluenesulfonic acid component is 0.07 to 0.65 mol / t and the content of the quaternary phosphonium component is 0.07 to 0.65 mol / t, relative to the total weight of the polyethylene terephthalate resin composition, as determined by liquid chromatography; the ratio of the content of the p-toluenesulfonic acid component to the content of the quaternary phosphonium component, i.e., the content of the p-toluenesulfonic acid component (mol / t) / the content of the quaternary phosphonium component (mol / t), is greater than 1.10 and is not more than 2.10; the content of phosphorus element is 2 to 20 ppm by weight, and the total content of manganese element and potassium element is 6 to 50 ppm by weight, relative to the total weight of the polyethylene terephthalate resin composition; When the polyethylene terephthalate resin composition treated under the following treatment conditions was observed with a scanning electron microscope, the content of coarse foreign matter having a circle equivalent diameter of 1 μm or more was 450 pieces / 0.1 mm 2 Below is the Polyethylene terephthalate resin composition. Treatment 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 at a vacuum of -0.1 MPa or less, atmospheric pressure of 60 ml / min, and output of 100 W for 5 minutes to expose large foreign matter. [2] The polyethylene terephthalate resin composition according to [1], further comprising a phosphorus-containing component other than the quaternary phosphonium component. [3] Melting resistivity is 5.0 x 10 6 The polyethylene terephthalate resin composition according to [1] or [2], having a modulus of elasticity of Ω·cm or less. [4] A polyester film formed from the polyethylene terephthalate resin composition according to any one of [1] to [3]. [5] The polyester film according to [4], which is used for any of magnetic recording material applications, release applications, and optical applications. [6] Step (a) esterifying terephthalic acid and ethylene glycol; Step (b) polycondensing the esterification reaction product in a polymerization apparatus; and step (c) adding a p-toluenesulfonic acid compound, a quaternary phosphonium compound, and at least one compound selected from a compound containing manganese and a compound containing potassium to the polymerization reactor during the period from the end of step (a) to the completion of the polycondensation reaction of step (b), a method for producing a polyethylene terephthalate resin composition, wherein in the step (c), the p-toluenesulfonic acid compound is added to the polymerization reactor separately from the quaternary phosphonium compound, the compound containing elemental manganese, and the compound containing elemental potassium, and the amounts of elemental phosphorus, elemental manganese, elemental potassium, the p-toluenesulfonic acid compound, and the quaternary phosphonium compound added relative to the total weight of the polyethylene terephthalate resin composition satisfy the following formulas (I) to (III): 2 ppm by weight or less of added phosphorus element ≦ 32 ppm by weight (I) 6 ppm by weight or less total amount of manganese and potassium added 50 ppm by weight or less (II) 0.6≦(amount of p-toluenesulfonic acid compound added (mol / t) / amount of quaternary phosphonium compound added (mol / t))≦1.1 (III) [Effects of the Invention]

[0008] The present invention provides a polyethylene terephthalate resin composition containing little foreign matter, having good color tone, excellent transparency, heat resistance, and good electrostatic applicability; a polyester film; and a method for producing the polyethylene terephthalate resin composition. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below. In this specification, "weight," "wt %," and "parts by weight" are synonymous with "mass," "mass %," and "parts by mass," respectively.

[0010] <Polyethylene terephthalate resin composition> A polyethylene terephthalate resin composition according to an embodiment of the present invention is a polyethylene terephthalate resin composition containing a p-toluenesulfonic acid component and a quaternary phosphonium component, the content of the p-toluenesulfonic acid component relative to the total weight of the polyethylene terephthalate resin composition, as determined by liquid chromatography, is 0.07 to 0.65 mol / t, and the content of the quaternary phosphonium component relative to the total weight of the polyethylene terephthalate resin composition is 0.07 to 0.65 mol / t; the ratio of the content of the p-toluenesulfonic acid component to the content of the quaternary phosphonium component, i.e., the content of the p-toluenesulfonic acid component (mol / t) / the content of the quaternary phosphonium component (mol / t), is greater than 1.10 and not more than 2.10; the content of phosphorus element is 2 to 20 ppm by weight, and the total content of manganese element and potassium element is 6 to 50 ppm by weight, relative to the total weight of the polyethylene terephthalate resin composition; When the polyethylene terephthalate resin composition treated under the following treatment conditions was observed with a scanning electron microscope, the content of coarse foreign matter having a circle equivalent diameter of 1 μm or more was 450 pieces / 0.1 mm 2 The following is the result. Treatment 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 at a vacuum of -0.1 MPa or less, atmospheric pressure of 60 ml / min, and output of 100 W for 5 minutes to expose large foreign matter.

[0011] The polyethylene terephthalate used in the present invention is obtained by esterifying terephthalic acid with ethylene glycol, followed by polycondensation, as described later in the method for producing the polyethylene terephthalate resin composition of the present invention. The molecular weight of the polyethylene terephthalate used in the present invention is preferably 16,000 to 20,000. The content of polyethylene terephthalate relative to the total weight of the polyethylene terephthalate resin composition of the present invention is preferably 95% by weight or more, more preferably 99% by weight or more.

[0012] The polyethylene terephthalate resin composition of the present invention must contain a p-toluenesulfonic acid component and a quaternary phosphonium component. By including the p-toluenesulfonic acid component and the quaternary phosphonium component in the polyethylene terephthalate resin composition, good electrostatic applicability can be obtained during film formation.

[0013] The polyethylene terephthalate resin composition of the present invention must have a p-toluenesulfonic acid component content of 0.07 to 0.65 mol / t relative to the total weight of the polyethylene terephthalate resin composition, as determined by liquid chromatography. A preferred range is 0.20 to 0.60 mol / t, and more preferably 0.25 to 0.50 mol / t. If the p-toluenesulfonic acid component content is less than 0.07 mol / t, the volume resistivity of the polyethylene terephthalate resin composition when molten increases, resulting in poor electrostatic castability during film formation. If the content exceeds 0.65 mol / t, color tone deteriorates and foreign matter due to the p-toluenesulfonic acid component is generated. The p-toluenesulfonic acid component of the present invention refers to the p-toluenesulfonic acid anion of a p-toluenesulfonic acid compound such as p-toluenesulfonic acid and its alkali metal salts. Examples of the p-toluenesulfonic acid compound used in the present invention include p-toluenesulfonic acid and its alkali metal salts, and among these, p-toluenesulfonic acid is preferred.

[0014] The polyethylene terephthalate resin composition of the present invention must have a quaternary phosphonium component content of 0.07 to 0.65 mol / t relative to the total weight of the polyethylene terephthalate resin composition, as determined by liquid chromatography. A preferred range is 0.10 to 0.49 mol / t, more preferably 0.15 to 0.33 mol / t. If the quaternary phosphonium component content is less than 0.07 mol / t, the ratio of the p-toluenesulfonic acid component to the quaternary phosphonium component in the polyethylene terephthalate resin composition will be high, resulting in the generation of foreign matter caused by the p-toluenesulfonic acid component. If the quaternary phosphonium component content exceeds 0.65 mol / t, the polyethylene terephthalate resin composition will have a high volume resistivity when melted, resulting in poor electrostatic castability during film formation.

[0015] The quaternary phosphonium component in the present invention refers to a quaternary phosphonium cation. As the quaternary phosphonium cation, a cation component in a quaternary phosphonium compound may be used. Examples of the quaternary phosphonium compound used in the present invention include hydroxides, chlorides, bromides, and other halides of tetraethylphosphonium, tetrabutylphosphonium, tetrahexylphosphonium, methyltributylphosphonium, ethyltributylphosphonium, octyltributylphosphonium, hexadecyltributylphosphonium, benzyltrimethylphosphonium, benzyltriethylphosphonium, and 3-(trifluoromethyl)phenyltrimethylphosphonium, and among these, tetrabutylphosphonium hydroxide (TBPH) is preferred.

[0016] The polyethylene terephthalate resin composition of the present invention must have a p-toluenesulfonic acid component content (mol / t) / quaternary phosphonium component content (mol / t) ratio of greater than 1.10. A preferred range is 1.40 or more, more preferably 1.70 or more. By making the content ratio of the p-toluenesulfonic acid component to the quaternary phosphonium component greater than 1.10, good electrostatic applicability can be obtained during film formation. If the ratio is less than 1.10, electrostatic applicability during film formation becomes poor. Furthermore, the content ratio must be 2.10 or less. A preferred range is 2.00 or less, and more preferably 1.90 or less. By setting the content ratio to 2.10 or less, it is possible to reduce the amount of coarse foreign matter having an equivalent circle diameter of 1 μm or more (hereinafter, sometimes simply referred to as coarse foreign matter) generated in the polyethylene terephthalate resin composition.

[0017] Detailed conditions for measuring the contents of p-toluenesulfonic acid and quaternary phosphonium components using liquid chromatography will be described in the Examples.

[0018] The polyethylene terephthalate resin composition of the present invention preferably further contains a phosphorus-containing component other than the quaternary phosphonium component. That is, the polyethylene terephthalate resin composition of the present invention preferably contains a quaternary phosphonium component and another phosphorus-containing component. Examples of phosphorus compounds used to incorporate the phosphorus-containing component other than the quaternary phosphonium component include one or more compounds selected from the group consisting of phosphoric acid, phosphorous acid, phosphonic acid, phosphonoacetic acid, or their methyl esters, ethyl esters, phenyl esters, and half esters. Two or more compounds may be mixed and used, and phosphoric acid is more preferred. By incorporating a phosphorus-containing component other than the quaternary phosphonium component, the heat resistance of the resulting polyethylene terephthalate resin composition can be further improved.

[0019] The polyethylene terephthalate resin composition of the present invention must contain 2 to 20 ppm by weight of phosphorus (atoms) relative to the total weight of the polyethylene terephthalate resin composition. A preferred range is 10 to 18 ppm by weight. If the phosphorus content is less than 2 ppm by weight, the color tone and heat resistance of the polyethylene terephthalate resin composition will be poor, and if it exceeds 20 ppm by weight, the electrostatic castability during film formation will be poor.

[0020] The polyethylene terephthalate resin composition of the present invention must have a total content of elemental manganese and elemental potassium of 6 to 50 ppm by weight relative to the total weight of the polyethylene terephthalate resin composition. A preferred range is 8 to 40 ppm by weight, and more preferably 10 to 30 ppm by weight. If the element (atom) content is less than 6 ppm by weight, the polyethylene terephthalate resin composition will gel, while if it exceeds 50 ppm by weight, the elemental manganese and elemental potassium will form metallic foreign matter, resulting in the generation of foreign matter and poor color tone.

[0021] The compound containing manganese element in the present invention is not particularly limited, but it is preferable to use manganese acetate, which may be a hydrate. The potassium-containing compound in the present invention is not particularly limited, but it is preferable to use potassium hydroxide.

[0022] The contents of phosphorus, manganese, and potassium in the polyethylene terephthalate resin composition of the present invention can be measured using a fluorescent X-ray analyzer. A specific method will be described in the Examples.

[0023] The polyethylene terephthalate resin composition of the present invention may further contain a catalyst. The catalyst is a catalyst used in the polycondensation reaction described below. Known polymerization catalysts can be used as catalysts for the polycondensation reaction of the polyethylene terephthalate resin composition of the present invention. Examples include oxides, carboxylates, acetates, hydroxides, chelate complexes, and alkoxides of antimony, titanium, aluminum, tin, germanium, zinc, cobalt, lead, manganese, and magnesium. These metal compounds may also be hydrates. From the viewpoint of polymerization time, it is preferable to use antimony compounds, titanium compounds, and germanium compounds as polymerization catalysts. Furthermore, from the viewpoint of suppressing foreign matter derived from metallic antimony, it is more preferable to use titanium compounds or germanium compounds as polymerization catalysts. These polymerization catalysts may be added in the form of powder, slurry, or solution, and are preferably added as a solution or slurry from the viewpoint of dispersibility. The solvent used here is preferably ethylene glycol.

[0024] When an antimony compound is used as a catalyst for the polycondensation reaction in the polyethylene terephthalate resin composition of the present invention, the content of elemental antimony is preferably in the range of 60 to 300 ppm by weight, more preferably 60 to 100 ppm by weight, relative to the total weight of the polyethylene terephthalate resin composition. By setting the content of elemental antimony to 60 ppm by weight or more, sufficient polymerization reactivity can be obtained, allowing polymerization to a predetermined degree of polymerization. By setting the content of elemental antimony to 300 ppm by weight or more, sufficient foreign matter derived from antimony metal is unlikely to be formed, thereby reducing the occurrence of defects in the film. Furthermore, from the viewpoint of reducing foreign matter derived from antimony metal, the content of elemental antimony is preferably 100 ppm by weight or less.

[0025] When a titanium compound is used as a catalyst for the polycondensation reaction in the polyethylene terephthalate resin composition of the present invention, the content of titanium element (atom) is preferably in the range of 0.1 to 20 ppm by weight, more preferably 0.1 to 7 ppm by weight, relative to the total weight of the polyethylene terephthalate resin composition, from the viewpoints of polymerization reactivity and activity against decomposition reaction.

[0026] When a germanium compound is used as a catalyst for the polycondensation reaction in the polyethylene terephthalate resin composition of the present invention, the content of germanium element is preferably in the range of 5 to 150 ppm by weight relative to the total weight of the polyethylene terephthalate resin composition, from the viewpoints of polymerization reactivity and activity against decomposition reaction.

[0027] The polyethylene terephthalate resin composition of the present invention can contain particles by a conventionally known method, as long as the effects of the present invention are not impaired. Examples of inorganic particles to be contained in the polyethylene terephthalate resin composition include 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, and silicon. Examples of organic particles include crosslinked polystyrene, crosslinked silicon, crosslinked acrylic, crosslinked styrene-acrylic, crosslinked polyester, polyimide, and melamine resin particles. However, the type of particle is not particularly limited. From the viewpoints of economy, thermal stability, and particle dispersibility, silica particles, alumina particles, and crosslinked polystyrene particles are preferred.

[0028] The method for incorporating particles into the polyethylene terephthalate resin composition of the present invention is not particularly limited, but from the viewpoint of improving particle dispersibility, it is preferable to incorporate particles into the polyethylene terephthalate resin composition by a method of adding the particles during the polycondensation reaction of the polyethylene terephthalate resin composition or by a method of kneading the particles with the polyethylene terephthalate resin composition after the polycondensation reaction using a twin-screw kneading extruder, etc. Furthermore, the number of particle types to be incorporated into the polyethylene terephthalate resin composition of the present invention is not particularly limited as long as the effects of the present invention are not impaired, and one or more types of particles can be incorporated.

[0029] The form of the particles to be contained in the polyethylene terephthalate resin composition of the present invention may be either a powder or a slurry, and from the viewpoint of dispersibility, it is preferable to add the particles as a slurry. The slurry may be either a water slurry or an ethylene glycol slurry, but from the viewpoint of particle dispersibility in the polyethylene terephthalate resin composition, it is preferable to add the particles as ethylene glycol.

[0030] The polyethylene terephthalate resin composition of the present invention is treated under the following conditions, and when the polyethylene terephthalate resin composition is observed with a scanning electron microscope (SEM), the content of coarse foreign matter having an equivalent circle diameter of 1 μm or more is 450 pieces / 0.1 mm 2 It must be less than 420 pieces / 0.1mm. 2 Less than 360 pieces / 0.1mm is more preferable 2 The number of large foreign objects is 450 / 0.1mm or less. 2 If the melting point exceeds 100° C., when the obtained polyethylene terephthalate resin composition is formed into a film, the film will have many defects. Treatment 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 at a vacuum of -0.1 MPa or less, atmospheric pressure of 60 ml / min, and output of 100 W for 5 minutes to expose large foreign matter. A specific method for measuring the content of coarse foreign matter will be explained in the Examples.

[0031] The polyethylene terephthalate resin composition of the present invention has a melt resistivity of 5.0×10 6 It is preferably Ω·cm or less, and more preferably 3.0×10 6 Ω·cm or less, more preferably 2.5×10 6 Ω·cm or less. Melting resistivity is 5.0×10 6 When the electrical resistance is Ω·cm or less, the polyethylene terephthalate resin composition can have good electrostatic applicability when being formed into a film.

[0032] <Method of producing polyethylene terephthalate resin composition> A method for producing a polyethylene terephthalate resin composition according to an embodiment of the present invention includes the steps of: Step (a) esterifying terephthalic acid and ethylene glycol; Step (b) polycondensing the esterification reaction product in a polymerization apparatus; and step (c) adding a p-toluenesulfonic acid compound, a quaternary phosphonium compound, and at least one compound selected from a compound containing manganese and a compound containing potassium to the polymerization reactor during the period from the end of step (a) to the completion of the polycondensation reaction of step (b), In the step (c), the p-toluenesulfonic acid compound is added to the polymerization reactor separately from the quaternary phosphonium compound, the compound containing elemental manganese, and the compound containing elemental potassium, and the amounts of elemental phosphorus, elemental manganese, elemental potassium, the p-toluenesulfonic acid compound, and the quaternary phosphonium compound added relative to the total weight of the polyethylene terephthalate resin composition satisfy the following formulas (I) to (III): 2 ppm by weight or less of added phosphorus element ≦ 32 ppm by weight (I) 6 ppm by weight or less total amount of manganese and potassium added 50 ppm by weight or less (II) 0.6≦(amount of p-toluenesulfonic acid compound added (mol / t) / amount of quaternary phosphonium compound added (mol / t))≦1.1 (III) The polyethylene terephthalate resin composition according to the embodiment of the present invention may be produced by the above-mentioned production method.

[0033] The method for producing a polyethylene terephthalate resin composition of the present invention includes a step of esterifying terephthalic acid and ethylene glycol (step (a)) and a step of polycondensing the esterification reaction product in a polymerization apparatus (step (b)). That is, the polyethylene terephthalate used in the present invention is obtained by esterifying terephthalic acid and ethylene glycol, followed by a polycondensation reaction.

[0034] In the method for producing a polyethylene terephthalate resin composition of the present invention, a p-toluenesulfonic acid compound, a quaternary phosphonium compound, and at least one compound selected from a compound containing manganese and a compound containing potassium must be added (step (c)) between the end of the esterification reaction (step (a)) and the completion of the polycondensation reaction (step (b)). From the viewpoint of uniformly mixing them into the polyethylene terephthalate resin composition, it is preferable to add them before the start of the polycondensation reaction.

[0035] In the method for producing a polyethylene terephthalate resin composition of the present invention, the p-toluenesulfonic acid compound must be added to the system separately from the quaternary phosphonium compound, the manganese-containing compound, and the potassium-containing compound. If the p-toluenesulfonic acid compound and the quaternary phosphonium compound are added to the system simultaneously, the dispersion will be poor, resulting in poor electrostatic castability during film formation. Furthermore, if the p-toluenesulfonic acid compound, the manganese-containing compound, and the potassium-containing compound are added to the system simultaneously, foreign matter will be generated due to the reaction of the compounds. It is preferable that the interval between the addition of the p-toluenesulfonic acid compound to the system and the addition of the quaternary phosphonium compound, the compound containing manganese element, and the compound containing potassium element be 3 minutes or more.

[0036] In the method for producing a polyethylene terephthalate resin composition of the present invention, as shown in (I) and (II), it is necessary to set the amount of phosphorus added to 2 to 32 ppm by weight, and the total amount of manganese and potassium added to 6 to 50 ppm by weight. By setting the above amounts, the content of phosphorus in the obtained polyethylene terephthalate resin composition can be set to 2 to 20 ppm by weight, and the total content of manganese and potassium can be set to 6 to 50 ppm by weight.

[0037] In the method for producing a polyethylene terephthalate resin composition of the present invention, as shown in (III), the ratio of the amount of p-toluenesulfonic acid compound (mol / t) to the amount of quaternary phosphonium compound (mol / t) must be 0.6 to 1.1. A ratio less than 0.6 results in poor electrostatic castability during film formation, while a ratio exceeding 1.1 results in the generation of foreign matter. In the production of the polyethylene terephthalate resin composition of the present invention, the quaternary phosphonium compound, in particular, is easily lost from the system due to scattering or sublimation during the reaction, causing the ratio of the p-toluenesulfonic acid component to the quaternary phosphonium component to fluctuate between the time of addition and the completion of the reaction of the polyethylene terephthalate resin composition. Therefore, by adjusting the amount of each compound to a specified range, the ratio of the p-toluenesulfonic acid component content (mol / t) to the quaternary phosphonium component content (mol / t) in the resulting polyethylene terephthalate resin composition can be set to a value greater than 1.10 and equal to or less than 2.10, thereby suppressing the generation of foreign matter in the polyethylene terephthalate resin composition and achieving good electrostatic castability.

[0038] The method for producing the polyethylene terephthalate resin composition of the present invention will be specifically described below.

[0039] First, terephthalic acid and ethylene glycol are charged into a reactor as raw materials and subjected to an esterification reaction to obtain an esterification product (hereafter referred to as BHT) composed of bishydroxyethyl terephthalate and its polymers. Next, this BHT is transferred to a polymerization vessel, where p-toluenesulfonic acid and a phosphorus-containing compound such as tetrabutylphosphonium are added separately. Next, at least one of a manganese-containing compound such as manganese acetate and a potassium-containing compound such as potassium hydroxide is added, followed by the addition of a conventional polymerization catalyst such as an antimony, germanium, or titanium compound. The temperature inside the vessel is slowly heated to 279°C and the pressure is reduced from atmospheric pressure to 133 Pa or less. The viscosity of the reactant increases as the polymerization reaction progresses. The reaction is terminated when a predetermined stirring torque is reached, and the polyethylene terephthalate resin composition is discharged from the polymerization vessel into a water tank. The discharged polyethylene terephthalate resin composition is quenched in the water tank and pelletized using a cutter.

[0040] The obtained polyethylene terephthalate resin composition is preferably pre-crystallized before the drying step. Pre-crystallization can be performed by applying a mechanical impact to the polyethylene terephthalate resin composition to perform a shearing treatment, or by performing a heat treatment under a hot air stream.

[0041] The polyethylene terephthalate resin composition of the present invention may be subjected to solid-state polymerization to obtain a high-molecular-weight polyethylene terephthalate resin composition. While the apparatus and method for solid-state polymerization are not particularly limited, the solid-state polymerization is carried out by heating the polyethylene terephthalate resin composition in an inert gas atmosphere or under reduced pressure at a temperature below the melting point of the polyethylene terephthalate resin composition. The inert gas may be any gas inert to the polyethylene terephthalate resin composition, such as nitrogen, helium, or carbon dioxide, although nitrogen is preferred for economic reasons. Furthermore, under reduced pressure conditions, achieving a higher vacuum is advantageous because it shortens the time required for the solid-state polymerization reaction; specifically, maintaining the pressure at 110 Pa or less is preferred.

[0042] The polyethylene terephthalate resin composition of the present invention can be suitably used in various applications such as films, fibers, and molded articles, and is particularly suitable for use in films due to its good electrostatic applicability and transparency. When the polyethylene terephthalate resin composition of the present invention is molded into a film, the film can be molded using a known molding method. When processing the polyethylene terephthalate resin composition of the present invention into a film, one or more additives, such as colorants including pigments and dyes, lubricants, antistatic agents, flame retardants, ultraviolet absorbers, antibacterial agents, nucleating agents, plasticizers, and mold release agents, can be added within a range that does not impair the effects of the present invention.

[0043] The film made from the polyethylene terephthalate resin composition of the present invention may be an unstretched film obtained by melt extrusion, or a stretched film obtained by uniaxial or biaxial stretching. Furthermore, when biaxial stretching is performed, the film may be a sequentially biaxially stretched film or a simultaneous biaxially stretched film. For example, pellets of the obtained polyethylene terephthalate resin composition are vacuum-dried at 180°C for at least 3 hours, then fed into an extruder heated to 280-320°C under a nitrogen stream or vacuum to prevent a decrease in intrinsic viscosity. The pellets are then passed through a fiber-sintered stainless steel metal filter, extruded through a slit die, and cooled while applying a static charge to the casting drum to obtain an unstretched film. This unstretched film is then introduced into an infrared heater and stretched between rolls in the longitudinal direction, i.e., the running direction of the film, to obtain a uniaxially stretched film. The uniaxially stretched film is then stretched in the width direction perpendicular to the longitudinal direction while being held with clips and heated, and then cooled to complete the crystal orientation, obtaining a sequentially biaxially stretched film. Alternatively, an unstretched film is stretched simultaneously in the longitudinal and transverse directions to obtain a simultaneously biaxially stretched film.

[0044] The film made of the polyethylene terephthalate resin composition of the present invention may be a single-layer film made entirely of the same resin, or may be a single-layer film made by blending the polyethylene terephthalate resin composition of the present invention with another polyester resin composition. It may also be a laminate film containing at least one film layer containing the polyethylene terephthalate resin composition of the present invention. When a film layer containing the polyethylene terephthalate resin composition of the present invention is laminated, the blending amount of the polyethylene terephthalate resin composition of the present invention is not particularly limited. Furthermore, from the viewpoint of imparting easy slippage to the resulting polyester film, a polyester resin composition containing particles may be blended.

[0045] The polyethylene terephthalate resin composition of the present invention has little foreign matter, good color tone, heat resistance, and good electrostatic applicability, and therefore can be suitably used for films for magnetic recording materials, films for release applications such as substrates for molding green sheets for multilayer ceramic capacitors, separators for liquid crystal polarizers, and substrates for dry film resists, and high-quality films for optical applications. Polyester films made from the polyester resin composition of the present invention are characterized by good electrostatic applicability during molding, little unevenness in film thickness, little metal foreign matter, and excellent transparency. The present invention also relates to a polyester film formed from the polyethylene terephthalate resin composition described above, and the polyester film used for any of magnetic recording material applications, release agents, and optical applications. [Example]

[0046] The present invention will be described in more detail below with reference to examples. The methods for measuring physical properties and evaluating effects were as follows.

[0047] (1) Intrinsic viscosity [η] of polyethylene terephthalate resin composition (unit: dl / g) 0.1 g of polyethylene terephthalate resin composition was weighed to within 0.001 g accuracy and dissolved in 10 mL of o-chlorophenol (OCP) by heating 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 placed in a water bath at 25 °C. The number of seconds it took for the viscometer to pass the marked line was measured (A seconds). Similarly, 8 mL of OCP alone was used in an Ostwald viscometer placed in a water bath at 25 °C. The number of seconds it took for the viscometer to pass the marked line was measured (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).

[0048] (2) p-toluenesulfonic acid component and quaternary phosphonium component content (unit: mol / t) 0.5 g of polyethylene terephthalate resin composition was dissolved in 8 mL of hexafluoroisopropanol, diluted with 10 mL of dichloromethane, and then 30 mL of methanol was slowly added to cause reprecipitation. Centrifugation was performed, and the supernatant was collected in a Daruma flask. The residue was washed with 10 mL of dichloromethane and 20 mL of methanol, and the supernatant was collected in the same Daruma flask. The Daruma flask was heated to 80°C while gently blowing in nitrogen gas. After concentration, the solution was diluted with dimethyl sulfoxide and used as a sample for liquid chromatography (hereinafter referred to as HPLC). The content (mol / t) of p-toluenesulfonic acid in the sample was determined using an HPLC system based on a previously prepared calibration curve for p-toluenesulfonic acid. The content (mol / t) of quaternary phosphonium compounds was also determined using an HPLC system based on previously prepared calibration curves for each substance (tetrabutylphosphonium hydroxide, tetraethylphosphonium hydroxide, or other quaternary phosphonium compounds). Liquid chromatography-mass spectrometry (LC-MS) analysis was used to identify each component separated by HPLC.

[0049] The HPLC measurement conditions are as follows. Manufacturer: HITACHI Model name: Chromaster (Detector: 5420, Column oven: 6310) Column: ODS-2 6.0 x 250 mm, 5 μm (GL Science) Mobile phase: A:B = 40:60 (A: 0.1% phosphoric acid aqueous solution, B: acetonitrile) Flow rate: 1.2mL / min Injection volume: 30μL Column temperature: 45℃ UV wavelength: 235nm

[0050] (3) Element (atom) content in polyethylene terephthalate resin composition (unit: weight ppm) The contents of phosphorus, manganese and potassium were calculated from a calibration curve prepared in advance by molding a sample pellet of the polyethylene terephthalate resin composition into a cylindrical shape using a melt press and measuring the fluorescent X-ray intensity using a Rigaku Corporation fluorescent X-ray analyzer (model number: 3270).

[0051] (4) Color b value of polyethylene terephthalate resin composition Resin pellets of the polyethylene terephthalate resin composition were filled into a cylindrical powder measurement cell, and the b value was measured using a reflection method with a color difference meter (SM Color Meter SM-T) manufactured by Suga Test Instruments Co., Ltd. (n=3). The arithmetic mean of the measured values ​​was taken as the color tone b value and used as an evaluation index for color tone. A value of 8.5 or less was considered good, a value of more than 8.5 and less than 9.0 was considered pass, and a value of more than 9.0 was considered fail.

[0052] (5) Melt resistivity of polyethylene terephthalate resin composition (unit: Ω cm) The polyethylene terephthalate resin composition was melted at 290°C and then subjected to a test on a 0.5 cm 2 Two stainless steel electrodes were inserted parallel to each other with an 8 mm gap between them, and after the temperature stabilized, the resistance value (R) was measured using a resistance meter (Hioki E.E. Corporation: Resistance Meter RM3545). Next, the melting resistivity (ρ) was calculated using the formula ρ (Ω·cm) = R × 0.5 / 0.8. This value was 2.5 × 10 6 Ω·cm or less is good, 2.5×106 Ω cm or greater than 5.0×10 6 Pass Ω cm or less, 5.0×10 6 If the resistance exceeded Ω·cm, it was deemed to have failed.

[0053] (6) Heat resistance of polyethylene terephthalate resin composition (main chain scission rate (%BB)) (unit: %) Five grams of polyethylene terephthalate resin composition was placed in a test tube and vacuum dried at 160°C for 5 hours. It was then melted in a 290°C oil bath for 6 hours under a 300 ml / min nitrogen flow. The intrinsic viscosity [η]6hr of the melt and the intrinsic viscosity [η]0hr before melting were used to calculate the main chain scission rate (%) = 0.27 × {[η]6hr^(-1.33) - [η]0hr^(-1.33)}. A value of 0.50% or less was considered good; a value greater than 0.50% but less than 0.55% was considered acceptable; and a value greater than 0.55% was considered unacceptable.

[0054] (7) Large foreign matter in polyethylene terephthalate resin composition (unit: piece / 0.1 mm 2 ) A polyethylene terephthalate resin composition was treated under the following conditions to prepare a measurement sample. Treatment 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 at a vacuum of -0.1 MPa or less, atmospheric pressure of 60 ml / min, and output of 100 W for 5 minutes to expose large foreign matter. The measurement sample was observed with a scanning electron microscope (SEM), and the images of the foreign matter were processed with an image analyzer. The SEM magnification was set to 1000x. Measurements were made at different observation points over an area of ​​0.1 square mm, and white matter with a circular equivalent diameter of 1 μm or more was considered foreign matter, and the number of foreign matter particles was counted. A total number of 360 or less per 0.1 square mm was considered good, 361 to 450 particles was considered acceptable, and 451 or more particles was considered unacceptable.

[0055] (8) Gelling rate of polyethylene terephthalate resin composition (unit: %) Resin pellets of a polyethylene terephthalate resin composition were pulverized using a freeze pulverizer (manufactured by Sprex CertiPerp) and weighed into a stainless steel beaker (0.5 g). After vacuum drying at 50°C for 2 hours using a vacuum dryer, the sample was adjusted to a 1% oxygen concentration with a mixture of air and nitrogen. The 1% oxygen concentration mixture was then passed through a pipe into the stainless steel beaker containing the weighed sample. The container was then immersed in a 300°C oil bath and heat-treated for 6 hours while a 1% oxygen concentration mixture of air and nitrogen was passed through at a flow rate of 0.5 L / min. The sample was dissolved in 20 ml of OCP at 160°C for 1 hour and allowed to cool. The solution was filtered using a glass filter (manufactured by Shibata Chemical Co., Ltd., 3GP40), and the glass filter was washed with dichloromethane. The glass filter was dried at 130°C for 2 hours, and the weight of the OCP insoluble matter (gel) remaining on the filter was calculated from the difference in weight between before and after filtration. The weight fraction of the OCP insoluble matter relative to the weight of polyethylene terephthalate was calculated and taken as the gelation rate (%). A gelation rate of 10% or less was considered good, a rate of 10% to 15% was considered pass, and a rate of more than 15% was considered fail.

[0056] (9) Polyester film forming properties When unstretched films were produced in the Examples and Comparative Examples, the film-forming properties were evaluated according to the following criteria. ○ (Good): The film was created without any problems. △ (pass): A decrease in adhesion to the casting drum was observed, but there was no problem with film production. × (fail): The adhesion to the casting drum was poor, making it difficult to produce a film.

[0057] (10) Total light transmittance of polyester film (unit: %) For films prepared by the methods described in the Examples and Comparative Examples, measurements were taken at three randomly selected locations on the film using an NDH-5000 manufactured by Nippon Denshoku Industries Co., Ltd. in accordance with JIS-K 7361 (1997), and the average value was calculated to be the total light transmittance (%). A value of 89.0% or higher was considered good, a value less than 89.0% but greater than or equal to 88% was considered pass, and a value below 88% was considered fail.

[0058] Example 1 A slurry consisting of 86 parts by weight of terephthalic acid and 37 parts by weight of ethylene glycol (1.15 times the molar ratio of terephthalic acid) was gradually added to an esterification reactor charged with 105 parts by weight of BHT melted at 250°C, and the esterification reaction was allowed to proceed while distilling off water. The temperature in the reaction system was controlled to 245-250°C, and the esterification reaction was terminated when the reaction rate reached 95%, and 105 parts by weight of the resulting BHT (equivalent to 100 parts by weight of PET) was charged in a molten state into a polymerization reactor equipped with a distillation device. After adding 0.0112 parts by weight of p-toluenesulfonic acid, the mixture was stirred for 5 minutes. 0.0077 parts by weight of tetrabutylphosphonium hydroxide (TBPH) was added as a quaternary phosphonium compound, and the mixture was stirred for another 5 minutes. Then, manganese acetate tetrahydrate (20 ppm by weight in terms of elemental manganese), 0.0024 parts by weight of phosphoric acid as a phosphorus compound other than the quaternary phosphonium compound, and 0.0084 parts by weight of diantimony trioxide were added. The amount of p-toluenesulfonic acid added was 0.41 mol / t, the amount of quaternary phosphonium added was 0.41 mol / t, and the ratio of the amount of p-toluenesulfonic acid added (mol / t) to the amount of quaternary phosphonium compound added (mol / t) was 1.0. The total amount of phosphorus added, including the quaternary phosphonium compound and other phosphorus compounds, was 20 ppm by weight. Subsequently, the pressure inside the polycondensation reaction tank was gradually reduced to 133 Pa or less over 35 minutes, and at the same time, the temperature was gradually increased to 279°C, and the polymerization reaction was carried out until the intrinsic viscosity of the polyethylene terephthalate resin composition reached 0.625 dL / g. Thereafter, the polycondensation reaction tank was returned to atmospheric pressure with nitrogen gas, and the composition was discharged into cold water from the die in the form of a strand and pelletized into cylindrical pellets using an extrusion cutter to obtain a polyethylene terephthalate resin composition.

[0059] The composition and properties of the obtained polyethylene terephthalate resin composition are shown in Tables 1, 3, and 4. The content of the p-toluenesulfonic acid component was 0.41 mol / t, the content of the quaternary phosphonium component was 0.22 mol / t, the p-toluenesulfonic acid component content (mol / t) / the quaternary phosphonium component content (mol / t) was 1.90, the color tone b value was 8.4, and the melt resistivity was 2.0 × 10 6 Ω·cm, %BB is 0.44%, and large foreign matter is 340 pieces / 0.1mm 2 The gelation rate was 9.8%, both of which were satisfactory.

[0060] The resulting resin pellets of the polyester resin composition were dried under reduced pressure at 160°C for 8 hours, then fed into an extruder and melt-extruded at 285°C. The resulting unstretched sheet was cast onto an electrostatically charged casting drum at 20°C. This unstretched sheet was stretched 3.5 times in the longitudinal direction using a stretching roll heated to 90°C, then stretched 4.0 times in the transverse direction at 120°C using a tenter-type stretching machine, and then heat-set at 230°C for 10 seconds. After uniformly and slowly cooling in a cooling zone, the sheet was wound up on a roll to obtain a polyester film with a thickness of 16 μm. The polyester film had good film-forming properties, and the total light transmittance of the obtained polyester film was 90.0%, which was good.

[0061] Example 2 A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 1, except that tetraethylphosphonium hydroxide was added as the quaternary phosphonium compound. The conditions and results are shown in Tables 1, 3, and 4. In Example 2, the color tone b value, %BB, coarse foreign matter, and gelation rate of the polyethylene terephthalate resin composition were good, and the melt resistivity was acceptable. In addition, the film-forming properties of the polyester film were good, and the total light transmittance of the obtained polyester film was good.

[0062] Examples 3 to 5 Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that the phosphorus compounds other than the quaternary phosphonium compound were changed as shown in Table 3. The conditions and results are shown in Tables 1, 3, and 4. In Examples 3 and 4, the color tone b value, melt resistivity, %BB, coarse foreign matter, and gelation rate of the polyethylene terephthalate resin compositions were good. The film-forming properties of the polyester films were also good, and the total light transmittance of the resulting polyester films was also good. In Example 5, the color tone b value, melt resistivity, and coarse foreign matter of the polyethylene terephthalate resin composition were good, and the %BB and gelation rate were acceptable. The film-forming properties of the polyester films were also good, and the total light transmittance of the resulting polyester films was also good.

[0063] (Examples 6 to 7) Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that the amount of phosphoric acid added was changed as shown in Table 3. The conditions and results are shown in Tables 1, 3, and 4. In Example 6, the amount of coarse foreign matter increased slightly due to the high content of phosphorus in the polyethylene terephthalate resin composition, but the test was acceptable. In Example 7, the gelation rate of the polyethylene terephthalate resin composition increased slightly due to the low content of phosphorus in the polyethylene terephthalate resin composition, but the test was acceptable.

[0064] (Examples 8 to 17) Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that the amounts of p-toluenesulfonic acid and tetrabutylphosphonium hydroxide added were changed as shown in Table 1. The conditions and results are shown in Tables 1, 3, and 4. In Examples 8 and 9, the amount of p-toluenesulfonic acid, quaternary phosphonium component, and phosphorus element was high, resulting in a slight increase in coarse foreign matter in the polyethylene terephthalate resin composition, but the film passed the test. In Example 9, the total light transmittance of the resulting polyester film also decreased, but the film passed the test. In Example 10, the amounts of p-toluenesulfonic acid, quaternary phosphonium component, and phosphorus element were low, but all properties were good. In Example 11, the amount of p-toluenesulfonic acid, quaternary phosphonium component, and phosphorus element was low, resulting in a slight increase in the melt resistivity of the polyethylene terephthalate resin composition, but the film passed the test. In Example 12, the p-toluenesulfonic acid component was high, and the p-toluenesulfonic acid component / quaternary phosphonium component ratio in the polyethylene terephthalate resin composition was high. This resulted in a slight increase in coarse foreign matter in the polyethylene terephthalate resin composition, and a slight decrease in the total light transmittance of the resulting polyester film, but the test passed. In Examples 13 and 14, the p-toluenesulfonic acid component was low, and the p-toluenesulfonic acid component / quaternary phosphonium component ratio in the polyethylene terephthalate resin composition was low, but all physical properties were good. In Examples 15 and 16, the amounts of the quaternary phosphonium component and phosphorus element were high, and the p-toluenesulfonic acid component / quaternary phosphonium component ratio in the polyethylene terephthalate resin composition was low, but all physical properties were good. In Example 17, the amounts of the quaternary phosphonium component and phosphorus element were low, and the p-toluenesulfonic acid component / quaternary phosphonium component ratio in the polyethylene terephthalate resin composition was high. This resulted in a slight increase in coarse foreign matter in the polyethylene terephthalate resin composition, and a slight decrease in the total light transmittance of the resulting polyester film, but the test passed.

[0065] (Examples 18 to 21) Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that the amount of manganese acetate tetrahydrate added was changed and the manganese content was set as shown in Table 3. The conditions and results are shown in Tables 1 to 4. In Examples 18 and 19, the amount of coarse foreign matter in the polyethylene terephthalate resin composition increased slightly due to the large amount of manganese. In Example 19, the %BB of the polyethylene terephthalate resin composition increased slightly, and the total light transmittance of the resulting polyester film decreased slightly, but the film passed the test. In Examples 20 and 21, the gelation rate of the polyethylene terephthalate resin composition increased slightly due to the small amount of manganese, but the film passed the test.

[0066] Examples 22 to 26 Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that potassium hydroxide was added instead of manganese acetate tetrahydrate so that the amount of potassium added was as shown in Table 3. The conditions and results are shown in Tables 2 to 4. In Examples 22 and 23, the color tone b value, melt resistivity, %BB, and coarse foreign matter of the polyethylene terephthalate resin composition were good, and the gelation rate was acceptable. The polyester film also had good film-forming properties, and the resulting polyester film had good total light transmittance. In Example 24, the color tone b value increased slightly but was acceptable, and all other physical properties were good. In Examples 25 and 26, the gelation rate of the polyethylene terephthalate resin composition increased slightly due to the small amount of potassium, and in Example 26, the melt resistivity of the polyethylene terephthalate resin composition decreased slightly but was acceptable, and all other physical properties were good.

[0067] (Comparative Example 1) The obtained esterification reaction product was charged into a polymerization apparatus, and then p-toluenesulfonic acid and tetrabutylphosphonium hydroxide were added simultaneously, followed by stirring for 5 minutes. A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 1, except that manganese acetate tetrahydrate, phosphoric acid, and diantimony trioxide were added. The conditions and results are shown in Tables 2 to 4. In Comparative Example 1, the p-toluenesulfonic acid compound and the quaternary phosphonium compound were added simultaneously, which resulted in poor dispersion of the compounds in the polyethylene terephthalate resin composition, causing uneven electrostatic application during casting onto a casting drum, and resulting in unacceptable film formability.

[0068] (Comparative Example 2) A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 1, except that the obtained esterification reaction product was charged into a polymerization apparatus, p-toluenesulfonic acid and manganese acetate tetrahydrate were added simultaneously and stirred for 5 minutes, tetrabutylphosphonium hydroxide was added and stirred for 5 minutes, and then phosphoric acid and diantimony trioxide were added. The conditions and results are shown in Tables 2 to 4. In Comparative Example 2, the p-toluenesulfonic acid compound and the compound containing manganese element were added simultaneously, which resulted in the generation of foreign matter, and the polyethylene terephthalate resin composition was rejected due to the large foreign matter.

[0069] (Comparative Example 3) A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 22, except that the obtained esterification reaction product was charged into a polymerization apparatus, p-toluenesulfonic acid and potassium hydroxide were added simultaneously and stirred for 5 minutes, tetrabutylphosphonium hydroxide was added and stirred for 5 minutes, and then phosphoric acid and diantimony trioxide were added. The conditions and results are shown in Tables 2 to 4. In Comparative Example 3, the p-toluenesulfonic acid compound and the potassium-containing compound were added simultaneously, which resulted in the generation of foreign matter, and the polyethylene terephthalate resin composition was rejected due to the large foreign matter.

[0070] Comparative Example 4 The resulting esterification reaction product was charged into a polymerization apparatus, and 0.0175 parts by weight of tetrabutylphosphonium p-toluenesulfonate was added, followed by stirring for 5 minutes. A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 1, except that manganese acetate tetrahydrate, phosphoric acid, and diantimony trioxide were added. The conditions and results are shown in Tables 2 to 4. In Comparative Example 4, the p-toluenesulfonic acid compound and the quaternary phosphonium compound were not added as separate compounds, resulting in poor dispersion of the compounds in the polyethylene terephthalate resin composition, which resulted in uneven electrostatic application during casting onto a casting drum and unacceptable film formability.

[0071] (Comparative Examples 5 to 7) A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 1, except that the amounts of p-toluenesulfonic acid and tetrabutylphosphonium hydroxide added were changed as shown in Table 3. The conditions and results are shown in Tables 2 to 4. In Comparative Example 5, the content of the p-toluenesulfonic acid component exceeded the specified range, so the color b value of the polyethylene terephthalate resin composition and the coarse foreign matter were unacceptable, and the total light transmittance of the resulting polyester film was unacceptable. In Comparative Example 6, the contents of the p-toluenesulfonic acid component and the quaternary phosphonium component were below the specified range, so the melt resistivity of the polyethylene terephthalate resin composition was unacceptable. In Comparative Example 7, the content of the quaternary phosphonium component was below the specified range, so the melt resistivity of the polyethylene terephthalate resin composition was unacceptable.

[0072] (Comparative Example 8) A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 1, except that the quaternary phosphonium compound was not added. The conditions and results are shown in Tables 2 to 4. In Comparative Example 8, the polyethylene terephthalate resin composition did not contain a quaternary phosphonium compound, and therefore failed in terms of melt resistivity and coarse foreign matter.

[0073] (Comparative Examples 9 to 12) Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that the amounts of p-toluenesulfonic acid and tetrabutylphosphonium hydroxide added were changed as shown in Table 1. The conditions and results are shown in Tables 2 to 4. In Comparative Examples 9 and 12, the ratios of the p-toluenesulfonic acid component and the quaternary phosphonium component in the polyethylene terephthalate resin composition exceeded the specified range, resulting in unacceptable coarse foreign matter in the polyethylene terephthalate resin composition and unacceptable total light transmittance in the resulting polyester film. In Comparative Examples 10 and 11, the ratios of the p-toluenesulfonic acid component and the quaternary phosphonium component in the polyethylene terephthalate resin composition were below the specified range, resulting in unacceptable melt resistivity in the polyethylene terephthalate resin composition and unacceptable film formability.

[0074] (Comparative Example 13) Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that the amount of phosphoric acid added was changed as shown in Table 3. The conditions and results are shown in Tables 2 to 4. In Comparative Example 13, the amount and content of phosphorus added exceeded the specified range, so the polyethylene terephthalate resin composition failed in terms of large foreign matter and the resulting polyester film failed in terms of total light transmittance. Furthermore, uneven electrostatic application occurred during casting onto the casting drum, resulting in unacceptable film formability.

[0075] (Comparative Examples 14 and 15) Polyethylene terephthalate resin compositions and polyester films were produced in the same manner as in Example 1, except that the amount of manganese acetate tetrahydrate added was changed and the manganese content was set as shown in Table 3. The conditions and results are shown in Tables 2 to 4. In Comparative Example 14, the total content of manganese and potassium exceeded the specified range, so the color b value, %BB, and coarse foreign matter of the polyethylene terephthalate resin composition were unacceptable. In Comparative Example 15, the total content of manganese and potassium was below the specified range, so the gelation rate of the polyethylene terephthalate resin composition was unacceptable.

[0076] (Comparative Examples 16 and 17) A polyethylene terephthalate resin composition and a polyester film were produced in the same manner as in Example 1, except that potassium hydroxide was added instead of manganese acetate tetrahydrate so that the amount of potassium added was as shown in Table 3. The conditions and results are shown in Tables 2 to 4. In Comparative Example 16, the total content of manganese and potassium exceeded the specified range, so the color tone b value of the polyethylene terephthalate resin composition failed. In Comparative Example 17, the total content of manganese and potassium was below the specified range, so the gelation rate of the polyethylene terephthalate resin composition failed.

[0077] [Table 1]

[0078] [Table 2]

[0079] [Table 3]

[0080] [Table 4]

Claims

1. A polyethylene terephthalate resin composition comprising a p-toluenesulfonic acid component and a quaternary phosphonium component, the content of the p-toluenesulfonic acid component is 0.07 to 0.65 mol / t and the content of the quaternary phosphonium component is 0.07 to 0.65 mol / t, relative to the total weight of the polyethylene terephthalate resin composition, as determined by liquid chromatography; the ratio of the content of the p-toluenesulfonic acid component to the content of the quaternary phosphonium component, i.e., the content of the p-toluenesulfonic acid component (mol / t) / the content of the quaternary phosphonium component (mol / t), is greater than 1.10 and is not greater than 2.10; the content of phosphorus element is 2 to 20 ppm by weight and the total content of manganese element and potassium element is 6 to 50 ppm by weight relative to the total weight of the polyethylene terephthalate resin composition; When the polyethylene terephthalate resin composition treated under the following treatment conditions was observed with a scanning electron microscope, the content of coarse foreign matter having a circle equivalent diameter of 1 μm or more was 450 pieces / 0.1 mm ２ Below is the Polyethylene terephthalate resin composition. Treatment conditions: Using a plasma reactor PR300 manufactured by Yamato Scientific Co., Ltd., the polyethylene terephthalate resin composition is removed by a plasma low-temperature ashing treatment method at a vacuum state of -0.1 MPa or less, air at 60 ml / min, and output of 100 W for 5 minutes to expose large foreign matter.

2. The polyethylene terephthalate resin composition according to claim 1, further comprising a phosphorus-containing component other than the quaternary phosphonium component.

3. Melting resistivity is 5.0 x 10 ６ The polyethylene terephthalate resin composition according to claim 1 or 2, having a modulus of elasticity of Ω·cm or less.

4. A polyester film formed from the polyethylene terephthalate resin composition according to any one of claims 1 to 3.

5. The polyester film according to claim 4, which is used for magnetic recording materials, release materials, or optical applications.

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