Polyester resin composition and polyester film made using the same

Abstract

To provide a polyester resin composition that has reduced foreign matter, a good color tone, good transparency (haze), heat resistance, and good electrostatic applicability.SOLUTION: A polyester resin composition contains sulfur element and phosphorus element. Relative to the weight of the polyester resin composition, the content of sulfur element is 2-20 wt.ppm and the content of phosphorus element is 2-20 wt.ppm, and the total content of calcium element, magnesium element, and manganese element is 5 wt.ppm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a polyester 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 issues, studies have been conducted as shown in the following documents. Patent Documents 1 and 2 propose a method of adding a large amount of an alkali metal compound, an alkaline earth metal compound, or a phosphorus compound to a polyester as a method of improving static electricity applicability. However, although this method can improve static electricity applicability to some extent, it has the problem of generating metal foreign matter due to the use of a large amount of magnesium acetate, which deteriorates transparency.

[0005] Patent Document 3 proposes a method of adding a quaternary phosphonium sulfonate as a method of improving electrostatic applicability, but because a large amount of alkali metal or alkaline earth metal is contained, this method is insufficient in suppressing metal foreign matter.

[0006] Patent Document 4 proposes a method for producing a polyester resin composition in which a sulfonic acid compound is added and no metal elements other than a polymerization catalyst are added. However, the amount of phosphoric acid added is large, and is insufficient to obtain electrostatic applicability for film formation. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-249213 [Patent Document 2] Japanese Patent Application Laid-Open No. 2008-201822 [Patent Document 3] Japanese Patent Application Laid-Open No. 2000-44703 [Patent Document 4] Japanese Patent Application Publication No. 10-36495 Summary of the Invention [Problem to be solved by the invention]

[0008] The above-mentioned conventional techniques have been insufficient to achieve both improved electrostatic applicability during film molding and reduced foreign matter derived from metal compounds. An object of the present invention is to provide a polyester resin composition that has little foreign matter, good color tone, excellent transparency (haze), heat resistance, and good electrostatic applicability. [Means for solving the problem]

[0009] As a result of extensive research to solve the above problems, the present invention has the following configuration. A polyester resin composition containing sulfur and phosphorus, characterized in that the sulfur content is 2 to 20 ppm by weight, the phosphorus content is 2 to 20 ppm by weight, and the total content of calcium, magnesium, and manganese is 5 ppm by weight or less, relative to the weight of the polyester resin composition. [Effects of the Invention]

[0010] The present invention provides a polyester resin composition which contains little foreign matter, has good color tone, is excellent in transparency (haze), and has heat resistance and good electrostatic applicability. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below.

[0012] The polyester resin composition used in the present invention refers to a polyester resin composition obtained by polycondensation of a dicarboxylic acid component and a diol component.

[0013] Examples of the dicarboxylic acid component of the present invention 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, etc. More preferred embodiments of the dicarboxylic acid of the present invention are terephthalic acid, 2,6-naphthalenedicarboxylic acid, isophthalic acid, or alkyl esters thereof, since they have a high melting point and can give polyester compositions that are easily processed into films, fibers, etc.

[0014] The diol component of the present invention may be any of aliphatic diols such as ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 2-methyl-1,3-propanediol, 1,2-hexanediol, 1,6-hexanediol, and neopentyl glycol; saturated alicyclic primary diols such as cyclohexanedimethanol, cyclohexanediethanol, norbornanedimethanol, norbornanediethanol, tricyclodecanedimethanol, tricyclodecanediethanol, decalindimethanol, and decalindiethanol; saturated heterocyclic primary diols containing cyclic ethers such as isosorbide; and other cycloaliphatic diols. Examples of suitable diols include various alicyclic diols such as cyclohexanediol, bicyclohexyl-4,4'-diol, 2,2-bis(4-hydroxycyclohexylpropane), 2,2-bis(4-(2-hydroxyethoxy)cyclohexyl)propane, cyclopentanediol, 3-methyl-1,2-cyclopentadiol, 4-cyclopentene-1,3-diol, and adamantanediol, and aromatic diols such as paraxylene glycol, bisphenol A, bisphenol S, styrene glycol, 9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene, and 9,9'-bis(4-hydroxyphenyl)fluorene. In addition to diols, polyfunctional alcohols such as trimethylolpropane and pentaerythritol can also be used as long as they do not impair the effects of the present invention. Among these, diols with a boiling point of 230°C or less are preferred because they can be easily distilled out of the reaction system, and aliphatic diols are more preferred because they are low cost and highly reactive. Furthermore, ethylene glycol is particularly preferred from the viewpoint of the mechanical properties of the resulting polyester resin composition and molded articles thereof.

[0015] The polyester resin composition of the present invention is not particularly limited, but preferably contains, as a main constituent, at least one structural unit selected from ethylene terephthalate, ethylene-2,6-naphthalate, propylene terephthalate, butylene terephthalate, hexamethylene terephthalate, cyclohexanedimethylene terephthalate, propylene-2,6-naphthalate, butylene-2,6-naphthalate, hexamethylene-2,6-naphthalate, and cyclohexanedimethylene-2,6-naphthalate units. Among these, polyesters containing ethylene terephthalate as a main constituent unit are particularly preferred due to their excellent moldability. Two or more polyesters may be mixed, or copolymerized polyesters may be used.

[0016] The polyester resin composition of the present invention contains elemental sulfur and elemental phosphorus, and the content of elemental sulfur is 2 to 20 ppm by weight, the content of elemental phosphorus is 2 to 20 ppm by weight, and the total content of elemental calcium, elemental magnesium, and elemental manganese is 5 ppm by weight or less, relative to the weight of the polyester resin composition. In the present invention, the term "element" may also be used to mean "atom" with respect to the content.

[0017] The polyester resin composition of the present invention preferably has a sulfur content of 2 to 20 ppm by weight, more preferably 9 to 17 ppm by weight, based on the weight of the polyester resin composition. As the sulfur content increases, better electrostatic applicability can be obtained during film molding. When the sulfur content is 2 ppm by weight or more, the volume resistivity of the polyester resin composition when molten decreases, resulting in better electrostatic castability during film molding. When the sulfur content is 20 ppm by weight or less, deterioration of color tone can be suppressed.

[0018] Examples of the compound containing sulfur element include sulfide compounds, thiophene compounds, thiol compounds, sulfonic acid compounds, sulfonyl compounds, etc. From the viewpoint of obtaining good electrostatic applicability when forming a film using the polyester resin composition, sulfonic acid compounds or sulfonyl compounds are preferred. Examples of sulfonic acid compounds include sulfonic acid compounds that do not have an ester-forming functional group, such as methanesulfonic acid, ethanesulfonic acid, 1-propanesulfonic acid, 1-butanesulfonic acid, 1-pentanesulfonic acid, trifluoromethanesulfonic acid, tetrafluoroethanesulfonic acid, nonafluorobutanesulfonic acid, benzenesulfonic acid, o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, 2,4,6-trimethylbenzenesulfonic acid, styrenesulfonic acid, perfluorooctane sulfonic acid, and heptadecafluorooctane sulfonic acid, as well as sulfonic acid compounds that have two or more ester-forming functional groups, such as 3,5-dicarboxybenzenesulfonic acid. These sulfonic acid compounds may also be used as alkali metal salts, quaternary phosphonium salts, or quaternary ammonium salts. Examples of sulfonyl compounds include perfluoroalkylsulfonylimides. Specific examples include perfluoroalkylsulfonimide salts such as potassium bis(trifluoromethanesulfonate)imide, sodium bis(trifluoromethanesulfonate)imide, sodium bis(nonafluorobutanesulfonyl)imide, and lithium bis(trifluoromethanesulfonate)imide.

[0019] Furthermore, the compound containing elemental sulfur is preferably a sulfonic acid compound represented by the following chemical formula (1).

[0020] [ka]

[0021] In chemical formula (1), A represents an aryl group having 6 to 7 carbon atoms, and X represents hydrogen, an alkali metal, a quaternary phosphonium cation, or a quaternary ammonium cation. Specific sulfonic acid compounds include benzenesulfonic acid, o-toluenesulfonic acid, m-toluenesulfonic acid, p-toluenesulfonic acid, or alkali metal salts, quaternary phosphonium salts, and quaternary ammonium salts thereof. Examples of alkali metals include lithium, sodium, and potassium. Examples of quaternary phosphonium cations include quaternary alkylphosphonium cations such as tetraethylphosphonium cation, tetrabutylphosphonium cation, tetrahexylphosphonium cation, methyltributylphosphonium cation, ethyltributylphosphonium cation, octyltributylphosphonium cation, and hexadecyltributylphosphonium cation; and quaternary arylalkylammonium cations such as benzyltrimethylphosphonium cation, benzyltriethylphosphonium cation, and 3-(trifluoromethyl)phenyltrimethylphosphonium cation. Examples of the quaternary ammonium cation include quaternary alkylammonium cations such as tetramethylammonium cation, tetraethylammonium cation, tetrapropylammonium cation, tetrabutylammonium cation, tetrahexylammonium cation, and hexadecyltrimethylammonium cation, and quaternary arylalkylammonium cations such as benzyltrimethylammonium cation, benzyltriethylammonium cation, and 3-(trifluoromethyl)phenyltrimethylammonium cation.

[0022] Among the sulfonic acid compounds represented by chemical formula (1), p-toluenesulfonic acid or its quaternary phosphonium salt is particularly preferred. Because the sulfonic acid compound represented by chemical formula (1) does not have an ester-forming functional group, it is dispersed in the polyester resin without being copolymerized therewith. This allows the polyester resin composition to have good electrostatic applicability during film formation without impairing its thermal properties, such as its melting point and glass transition point. Furthermore, because it does not have an ester-forming functional group, it can suppress the coarsening of foreign matter derived from the sulfonic acid compound, even if such foreign matter forms. Furthermore, using a linear alkyl group having 6 or more carbon atoms or an aryl group having 8 or more carbon atoms as A in chemical formula (1) is undesirable because it increases the foaming of the cold water during the process of discharging the polyester resin composition in strand form from a polycondensation reaction vessel into cold water and pelletizing it, thereby reducing productivity. The sulfonic acid compound represented by chemical formula (1) is preferably contained in the polyester resin composition in an amount of 1 to 12 mmol% relative to the acid component of the polyester, from the viewpoints of imparting good electrostatic applicability during film molding, obtaining a polyester resin composition with good color tone, and suppressing coarsening of foreign matter derived from the sulfonic acid compound.

[0023] The method for incorporating elemental sulfur into the polyester resin composition of the present invention is not particularly limited. One or more compounds containing elemental sulfur can be incorporated into the polyester resin composition by known methods, such as adding one or more compounds containing elemental sulfur during the polycondensation reaction of the polyester resin composition or kneading the compounds with the polyester resin composition after the polycondensation reaction using a twin-screw kneading extruder or the like.

[0024] The polyester resin composition of the present invention has a phosphorus content of 2 to 20 ppm by weight, preferably 2 to 10 ppm by weight, based on the weight of the polyester resin composition. When the phosphorus content is 2 ppm by weight or more, the polyester resin composition has good color tone and heat resistance, and when it is 20 ppm by weight or less, the polyester resin composition has good electrostatic castability during film formation.

[0025] The method for incorporating phosphorus into the polyester resin composition of the present invention is not particularly limited. One or more known compounds containing phosphorus can be used, such as phosphoric acid, trimethyl phosphate, ethyl diethyl phosphonoacetate, phosphorous acid, alkali metal phosphates, and salts with a quaternary phosphonium cation. These phosphorus compounds can be incorporated into the polyester resin composition by known methods, such as adding them during the polycondensation reaction of the polyester resin composition or kneading them with the polyester resin composition after the polycondensation reaction using a twin-screw kneading extruder.

[0026] In order to prevent the formation of foreign matter between the sulfonic acid compound and calcium ions, magnesium ions, and manganese ions, the polyester resin composition of the present invention must have a total content of calcium, magnesium, and manganese of 5 ppm by weight or less based on the total polyester resin composition. By ensuring that the total content of calcium, magnesium, and manganese is 5 ppm by weight or less, a polyester resin composition with good color tone and solution haze and little foreign matter can be obtained. Furthermore, in order to prevent the formation of foreign matter, it is more preferable that the polyester resin composition does not contain calcium, magnesium, or manganese.

[0027] When calcium, magnesium, or manganese is added to the polyester resin composition of the present invention, the method is not particularly limited. However, it is preferable to add the calcium compound, magnesium compound, or manganese compound during the polycondensation reaction of the polyester resin composition. The calcium compound, magnesium compound, or manganese compound may be added in the form of powder, slurry, or solution, although adding the compound as a solution is preferable from the viewpoint of dispersibility. In this case, the solvent is preferably the same as that of the diol component of the polyester composition. Examples of calcium compounds include calcium acetate, calcium propionate, calcium chloride, calcium bromide, calcium iodide, and calcium hydroxide. Examples of magnesium compounds include magnesium acetate, magnesium propionate, magnesium chloride, magnesium bromide, magnesium iodide, and magnesium hydroxide. Examples of manganese compounds include manganese acetate, manganese propionate, manganese chloride, manganese bromide, manganese iodide, and manganese hydroxide.

[0028] Known polymerization catalysts can be used as catalysts for the polycondensation reaction of the polyester 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 in this case is preferably the same as that used for the diol component of the polyester composition.

[0029] When an antimony compound is used as a catalyst for the polycondensation reaction in the polyester 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 weight of the polyester resin composition. If the content of elemental antimony is less than 60 ppm by weight, the polymerization reactivity is insufficient and polymerization to the predetermined degree of polymerization cannot be achieved. If the content of elemental antimony exceeds 300 ppm by weight, foreign matter derived from antimony metal is formed, which becomes a defect in the film, and is therefore undesirable. 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.

[0030] When a titanium compound is used as a catalyst for the polycondensation reaction in the polyester resin composition of the present invention, the content of titanium element 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 weight of the polyester resin composition, from the viewpoints of polymerization reactivity and activity in decomposition reactions.

[0031] When a germanium compound is used as a catalyst for the polycondensation reaction in the polyester 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 weight of the polyester resin composition, from the viewpoints of polymerization reactivity and activity against decomposition reaction.

[0032] The polyester resin composition of the present invention may contain particles. Examples of particles contained in the polyester resin composition of the present invention include inorganic particles such as 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, and organic particles such as crosslinked polystyrene, crosslinked silicon, crosslinked acrylic, crosslinked styrene-acrylic, crosslinked polyester, polyimide, and melamine resin particles, but the type of particle is not particularly limited. From the viewpoints of economy, thermal stability, and particle dispersibility, it is preferable to use silica particles, alumina particles, and crosslinked polystyrene particles.

[0033] When inorganic particles are incorporated into the polyester resin composition of the present invention, the content of the inorganic particles is not particularly limited, but is preferably in the range of 0.001 to 6.5 wt% of the polyester resin composition from the viewpoints of particle dispersibility and excellent anti-blocking properties when molded into a product. Furthermore, the volume particle size of the inorganic particles is not particularly limited, but from the viewpoint of particle dispersibility, it is preferred that the volume average particle size be in the range of 1.0 to 5.0 μm for aggregated silica particles, 0.05 to 0.5 μm for colloidal silica particles, or 0.01 to 1.0 μm for alumina particles.

[0034] When organic particles are contained in the polyester resin composition of the present invention, the content of the organic particles is not particularly limited, but is preferably in the range of 0.001 to 5.0 wt% of the polyester resin composition from the viewpoints of particle dispersibility and excellent anti-blocking properties when formed into a molded article. Furthermore, the particle size of the organic particles is not particularly limited, but in the case of crosslinked polystyrene particles, a volume average particle size in the range of 0.1 to 1.5 μm is preferred from the viewpoint of particle dispersibility.

[0035] 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 particles into the polyester resin composition by a method of adding them during the polycondensation reaction of the polyester resin composition or a method of kneading them with the polyester resin composition after the polycondensation reaction using a twin-screw kneading extruder, etc. Furthermore, the number of particle types to be incorporated into the polyester 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.

[0036] The form of the particles contained in the polyester 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 them as a slurry. 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 the slurry is the same as the diol component of the polyester composition. Below, a method for producing the polyester resin composition of the present invention will be specifically described. For example, when the polyester resin composition of the present invention is polyethylene terephthalate, it is usually produced by a process in which terephthalic acid or dimethyl terephthalate and ethylene glycol are used as raw materials, and a low polymer such as bishydroxyethyl terephthalate (hereinafter referred to as BHT) is obtained by a reaction such as an esterification reaction or a transesterification reaction, and then a high molecular weight PET is obtained by a polycondensation reaction.

[0037] The reaction for obtaining low polymer BHT is not particularly limited and can be carried out by known reactions, but an esterification reaction is preferred because the reaction proceeds sufficiently even without a catalyst due to the autocatalytic action of the carboxylic acid, eliminating the need to add reaction catalysts such as calcium compounds, magnesium compounds, manganese compounds, etc. By carrying out the esterification reaction without a catalyst, it is possible to suppress thermal decomposition and the generation of foreign matter in the polycondensation reaction stage.

[0038] The polyester resin composition of the present invention can contain an alkali metal element within a range that does not impair the effects of the present invention, thereby improving the heat resistance of the polyester resin composition. To incorporate an alkali metal element into the polyester resin composition of the present invention, an alkali metal compound is used. Examples of the alkali metal compound include lithium acetate, alkali metal hydroxides such as lithium hydroxide, sodium hydroxide, and potassium hydroxide, alkali metal phosphate salts such as sodium dihydrogen phosphate, disodium hydrogen phosphate, trisodium phosphate, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, and tripotassium phosphate, and alkali metal salts of sulfonic acid compounds such as sodium methanesulfonate, potassium methanesulfonate, sodium butylsulfonate, potassium butylsulfonate, sodium trifluoromethanesulfonate, potassium trifluoromethanesulfonate, sodium tetrafluoroethanesulfonate, and tetrafluoroethanesulfonic acid. Examples include potassium, sodium nonafluorobutanesulfonate, potassium nonafluorobutanesulfonate, sodium benzenesulfonate, potassium benzenesulfonate, sodium p-toluenesulfonate, potassium p-toluenesulfonate, sodium 2,4,6-trimethylbenzenesulfonate, potassium 2,4,6-trimethylbenzenesulfonate, sodium styrenesulfonate, potassium styrenesulfonate, sodium perfluorooctane sulfonate, potassium perfluorooctane sulfonate, sodium heptadecafluorooctane sulfonate, and potassium heptadecafluorooctane sulfonate.

[0039] These alkali metal compounds can be incorporated into the polyester resin composition by known methods, such as adding them during the polycondensation reaction of the polyester resin composition or kneading them with the polyester resin composition after the polycondensation reaction using a twin-screw kneading extruder or the like.

[0040] Thereafter, the resulting molten polyester is discharged in the form of a strand from a die, cooled, and pelletized with a cutter, thereby producing a polyester resin composition.

[0041] The obtained polyester resin composition is preferably pre-crystallized before the drying step. Pre-crystallization can be performed by applying a mechanical impact to the polyester resin composition to perform a shearing treatment, or by performing a heat treatment under a hot air stream.

[0042] The polyester composition of the present invention may be subjected to solid-state polymerization to obtain a high-molecular-weight polyester resin composition. While the apparatus and method for solid-state polymerization are not particularly limited, the polyester composition is typically heated under an inert gas atmosphere or reduced pressure at a temperature below the melting point of the polyester resin composition. Any inert gas may be used as long as it is inert to the polyester resin composition, such as nitrogen, helium, or carbon dioxide. However, nitrogen is preferred for economic reasons. Under reduced pressure conditions, achieving a higher vacuum is advantageous because it shortens the time required for the solid-state polymerization reaction; specifically, maintaining a pressure of 110 Pa or less is preferred.

[0043] The polyester 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 excellent electrostatic applicability and transparency. When molding the polyester resin composition of the present invention into a film, the film can be molded using a known molding method. When processing the polyester 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, UV 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.

[0044] Films made from the polyester resin composition of the present invention may be unstretched films obtained by melt extrusion, or may be stretched films obtained by uniaxial or biaxial stretching. Furthermore, when biaxial stretching is performed, sequential biaxial stretching or simultaneous biaxial stretching may be used. For example, pellets of the obtained polyester 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 sintered-fiber 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, a simultaneously biaxially stretched film can be obtained by simultaneously stretching an unstretched film in the longitudinal and transverse directions.

[0045] The film made of the polyester 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 polyester 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 polyester resin composition of the present invention. When a film layer containing the polyester resin composition of the present invention is laminated, the blending amount of the polyester 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.

[0046] The polyester resin composition of the present invention has few foreign matters, good color tone, excellent transparency (haze), heat resistance, and good electrostatic applicability, and therefore can be suitably used for 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, as well as 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. [Example]

[0047] 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.

[0048] (1) Intrinsic viscosity [η] of polyester resin composition (unit: dl / g) 0.1 g of polyester 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 25 °C water bath. 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 25 °C water bath and 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).

[0049] (2) Element content in polyester resin composition (unit: ppm by weight) The contents of phosphorus, magnesium, manganese, calcium, antimony, titanium, and germanium were calculated from a calibration curve prepared in advance by molding a sample pellet of the polyester resin composition into a cylindrical shape using a melt press and measuring the fluorescent X-ray intensity using a fluorescent X-ray analyzer (model number: 3270) manufactured by Rigaku Corporation.

[0050] Regarding the sulfur element content, resin pellets of the polyester resin composition were combusted using an automatic sample combustion device (model number: AQF-2100) manufactured by Mitsubishi Chemical Analytech Co., Ltd., and the generated gas was absorbed into a solution, after which a portion of the absorbed solution was analyzed by an ion chromatography (model number: ICS1600) manufactured by DIONEX Corp. The sample was weighed and measured twice, and the average value of the measured values ​​was taken as the sulfur element content.

[0051] (3) Color tone of polyester resin composition Resin pellets of the polyester 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 greater than 8.5 and less than 9.0 was considered pass, and a value greater than 9.0 was considered fail.

[0052] (4) Melt resistivity of polyester 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 (R) was measured using a resistance meter (Hioki E.E. Corporation: Resistance Meter RM3545).The melting resistivity (ρ) was then calculated using the formula ρ (Ω·cm) = R × 0.5 / 0.8. This value is 4.0 × 10 6 Ω·cm or less is good, 4.0×10 6 Ω cm or greater than 9.0×10 6 Pass Ω cm or less, 9.0×10 6 If the resistance exceeded Ω·cm, it was deemed to have failed.

[0053] (5) Heat resistance of polyester resin composition (main chain scission rate (%BB)) (unit: %) Five grams of polyester resin composition was placed in a test tube and vacuum dried at 160°C for five hours. It was then melted in a 290°C oil bath for six 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 (%) using the formula: Main Chain Scission Rate (%) = 0.27 × {[η]6hr^(-1.33) - [η]0hr^(-1.33)}. A value of 0.40% or less was considered acceptable, and a value above 0.40% was considered unacceptable.

[0054] (6) Solution haze of polyester resin composition (unit: %) 2.0 g of the polyester resin composition was dissolved in 20 mL of a phenol / 1,1,2,2-tetrachloroethane (60:40 wt%) mixed solvent at 100°C for 60 minutes with stirring. After cooling to room temperature, the solution was placed in a 20 mm glass cell and measured using a Suga Test Instruments Haze Computer (HGM-2DP). If the solution haze measurement was 0.5% or less, the polyester resin composition had excellent transparency; if it was greater than 0.5% and less than 0.8%, it had good transparency; if it was greater than 0.8% and less than 40%, it was considered pass; and if it exceeded 40%, it was considered fail.

[0055] (7) Large foreign matter in polyester resin composition (unit: piece / 0.1 mm 2 ) The polyester resin composition is removed using a plasma low-temperature ashing process to expose large foreign particles. Processing conditions are selected to minimize damage to the foreign particles. The foreign particles are observed using a scanning electron microscope (SEM), and the foreign particle images are processed using an image analyzer. A magnification of 1000x is selected for the SEM. Measurements are taken over an area of ​​0.1 square mm at different observation points, and foreign particles with a circular equivalent diameter of 1 μm or more are counted for the white material excluding the added particle components. A total number of 180 or less per 0.1 square mm is considered good, 181 to 250 is considered acceptable, and 251 or more is considered unacceptable.

[0056] (8) Film-forming properties of polyester resin composition 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] (9) 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 represent the total light transmittance (%). A value of 92.0% or higher was considered excellent, a value of less than 92.0% but 91.0% or higher was considered good, a value of less than 91.0% but 60% or higher was considered pass, and a value below 60% was considered fail.

[0058] (10) Volume average particle size of particles (unit: μm) The EG dispersion of particles was diluted with water and the particle size distribution was measured using a laser diffraction / scattering particle size distribution analyzer (LA700 manufactured by Horiba, Ltd.). The concentration was adjusted by dilution with water to a light transmittance of 80-95%, and the particle size at an integrated volume fraction of 50% in the equivalent sphericity distribution measured at a measurement temperature of 25°C and a circulation rate of 570 mL / min was taken as the volume-average particle size.

[0059] (11) Particle content in polyester resin composition (unit: wt%) A sample pellet of the polyester resin composition was dissolved in 200 mL of a potassium hydroxide / methanol mixed solution by stirring at 120° C. for 120 minutes, then cooled and centrifuged, and the solid content was weighed, and the content was calculated from the weight value.

[0060] (12) Melting point of polyester resin composition (unit: °C) In accordance with JIS K 7121 (1999), a differential scanning calorimeter "Robot DSC-RDC220" manufactured by Seiko Instruments, Inc. was used, and a disc session "SSC / 5200" was used for data analysis. Five mg of sample was weighed into a sample pan, and the sample was heated from 25°C to 300°C at a heating rate of 16°C / min (1st run), held at that temperature for 5 minutes, and then rapidly cooled to 25°C or below. Immediately following this, the sample was again heated from 25°C to 300°C at a heating rate of 16°C / min, and measurements were performed. A differential scanning calorimetry chart (vertical axis represents heat energy, horizontal axis represents temperature) was obtained for the 2nd run. The peak top temperature of the crystalline melting peak, which is an endothermic peak, was determined and used as the melting point. When two or more crystalline melting peaks were observed, the melting point was determined as the peak top temperature with the largest peak area. If this value was between 253.5°C and 256.0°C, it was judged as passing, and anything else was judged as failing.

[0061] (13) Sulfonic acid compound content in polyester resin composition (unit: mmol%) 0.5 g of polyester 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. The mixture was centrifuged 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 mixture was diluted with dimethyl sulfoxide and used as a sample for liquid chromatography (hereinafter referred to as HPLC). The sulfonic acid compound content (mmol%) in the sample was determined using an HPLC device.

[0062] 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.

[0063] In the following, Examples 13, 24 to 26, and 28 will be read as Reference Examples 13, 24 to 26, and 28, respectively. 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 to terephthalic acid) was gradually added to an esterification reactor containing 105 parts by weight of melted BHT 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 esterification product (equivalent to 100 parts by weight of PET) was charged in a molten state into a polymerization reactor equipped with a distillation device.

[0064] 0.0084 parts by weight of diantimony trioxide and 0.0175 parts by weight of tetrabutylphosphonium p-toluenesulfonate were added as ethylene glycol solutions, and the pressure in the polymerization reaction vessel was gradually reduced to 0.13 kPa or less over 35 minutes, while the temperature was gradually increased to 279°C, and the polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.625. Thereafter, the polycondensation reaction vessel was returned to normal pressure with nitrogen gas, and the mixture was discharged into cold water in the form of a strand from a die and pelletized into cylindrical pellets using an extrusion cutter to obtain a polyester resin composition. The obtained polyester resin composition was confirmed to contain the sulfur, phosphorus, and antimony elements in the amounts shown in Table 1, and to contain 8 mmol% of sulfonic acid compounds. The color tone b value was 8.3, and the melt resistivity was 2.2 × 10 6 Ω·cm, main chain scission rate of heat resistance index is 0.33%, coarse foreign matter of 1μm or more is 120 pieces / 0.1mm 2 The solution haze was 0.3%, which was excellent.

[0065] 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 excellent at 92.7%.

[0066] (Examples 2 and 3) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that sodium p-toluenesulfonate and trimethyl phosphate were added instead of tetrabutylphosphonium p-toluenesulfonate, and the sulfur and phosphorus contents were set as shown in Table 1. The results are shown in Table 2. In Example 2, the melt resistivity increased due to the increased sulfur content compared to the polyester resin composition of Example 1, but was still within a good range. The polyester film obtained was also evaluated as excellent or good. In Example 3, the sulfur element content was increased compared to the polyester resin composition of Example 2, and the melt resistivity also increased, but was still within the acceptable range. In addition, there was no problem with the film-forming properties of the polyester film.

[0067] (Comparative Example 1) A polyester resin composition was obtained in the same manner as in Example 1, except that trimethyl phosphate was added instead of tetrabutylphosphonium p-toluenesulfonate, and the phosphorus content was set as shown in Table 1. The results are shown in Table 2. The resulting polyester resin composition did not contain sulfur element, and therefore failed in melt resistivity. In addition, there was a problem with adhesion to the casting drum during polyester film production, and polyester film could not be obtained.

[0068] (Examples 4 to 6, Comparative Example 2) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that sodium p-toluenesulfonate was added in addition to diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate, so that the sulfur and phosphorus contents were as shown in Table 1. The results are shown in Table 2. The polyester resin composition and polyester film of Example 4 were excellent or good in all the indices. In Example 5, the color tone b value was larger but still within the acceptable range because the polyester resin composition contained more sulfur element than in Example 1. The polyester film obtained was evaluated as excellent or good. In Example 6, the heat resistance was worsened but still within the acceptable range because the content of phosphorus element was lower than that of the polyester resin composition of Example 1. In addition, the polyester film obtained was evaluated as excellent or good. In Comparative Example 2, the obtained polyester resin composition contained a large amount of sulfur element, and therefore the color tone b value was unacceptable.

[0069] Examples 7 to 9 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that trimethyl phosphate was added in addition to diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate, and the sulfur and phosphorus contents were set as shown in Table 1. The results are shown in Table 2. In Example 7, the polyester resin composition and polyester film obtained were excellent or good in all evaluations. In Examples 8 and 9, the melt resistivity increased because the phosphorus content was higher than that of the polyester resin composition of Example 1, but was still within the acceptable range. In addition, there was no problem with the film-forming properties of the polyester film.

[0070] (Comparative Example 3) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that sodium p-toluenesulfonate was added instead of tetrabutylphosphonium p-toluenesulfonate, and the sulfur element content was set as shown in Table 1. The results are shown in Table 2. The polyester resin composition obtained did not contain phosphorus element, and therefore failed the color tone b value, heat resistance, and number of large foreign matter.

[0071] Comparative Example 4 A polyester resin composition was obtained in the same manner as in Example 1, except that trimethyl phosphate was added in addition to diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate, and the sulfur and phosphorus contents were as shown in Table 1. The results are shown in Table 2. The obtained polyester resin composition had a high phosphorus content and failed in melt resistivity. In addition, there was a problem with adhesion to the casting drum during polyester film production, and a polyester film could not be obtained.

[0072] [Table 1]

[0073] [Table 2]

[0074] (Example 10, Comparative Example 5) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that calcium acetate monohydrate was added in addition to diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate to achieve the sulfur, phosphorus, and calcium element contents shown in Table 3. The results are shown in Table 4. In Example 10, calcium element was contained compared to the polyester resin composition of Example 1, so the color tone b value, solution haze, and coarse foreign matter increased, but all were within the acceptable range. In addition, there were no problems in the evaluation of the obtained polyester film. In Comparative Example 5, the polyester resin composition contained a larger amount of calcium element than in Example 10, and therefore failed in the color tone b value and coarse foreign matter.

[0075] (Example 11, Comparative Example 6) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that magnesium acetate tetrahydrate was added in addition to diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate to achieve the contents of sulfur, phosphorus, and magnesium shown in Table 3. The results are shown in Table 4. In Example 11, the color tone b value, solution haze, and coarse foreign matter increased because magnesium element was contained compared to the polyester resin composition of Example 1, but all were within the acceptable range. In addition, there were no problems in the evaluation of the obtained polyester film. In Comparative Example 6, the magnesium element was contained in a larger amount than in the polyester resin composition of Example 11, and therefore, the color tone b value and coarse foreign matter were unacceptable.

[0076] (Example 12, Comparative Example 7) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that manganese acetate tetrahydrate was added in addition to diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate to achieve the contents of sulfur, phosphorus, and manganese shown in Table 3. The results are shown in Table 4. In Example 12, the color tone b value, solution haze, and coarse foreign matter increased because manganese was contained compared to the polyester resin composition of Example 1, but all were within the acceptable range. In addition, there were no problems in the evaluation of the obtained polyester film. In Comparative Example 7, the polyester resin composition contained a larger amount of manganese element than in Example 12, and therefore failed in the color tone b value and coarse foreign matter.

[0077] Example 13 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that instead of adding tetrabutylphosphonium p-toluenesulfonate, tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate, a copolymerization component, was added, and the sulfur and phosphorus contents were as shown in Table 3. Because sulfonic acid compounds were copolymerization components, they could not be detected by method (13). The results of the property evaluation are shown in Table 4. The obtained polyester resin composition contained more coarse foreign matter than the polyester resin composition of Example 1, but was within the acceptable range, and the total light transmittance of the polyester film was also low, but was within the acceptable range.

[0078] (Comparative Example 8) Instead of the esterification reaction, 100 parts by weight of dimethyl terephthalate, 70 parts by weight of ethylene glycol, and manganese acetate tetrahydrate were charged into a reactor so that the manganese element amount was 85 ppm by weight relative to the polyester resin composition, and the contents were dissolved at 150°C. After that, the temperature of the reaction contents was slowly raised to 230°C while stirring, and methanol was distilled off to a predetermined amount to carry out a transesterification reaction, thereby obtaining a low polymer BHT. After the polycondensation reaction, a polyester resin composition and a polyester film were obtained in the same manner as in Example 1. The obtained polyester resin composition contained the sulfur element, phosphorus element, and manganese element in the amounts shown in Table 3. As shown in Table 4, the obtained polyester resin composition failed in color tone b value and heat resistance, and the amount of coarse foreign matter was far outside the acceptable range due to the high manganese element content.

[0079] (Comparative Example 9) 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 containing 105 parts by weight of BHT dissolved 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 esterification product (equivalent to 100 parts by weight of PET) was charged in a molten state into a polymerization reactor equipped with a distillation device.

[0080] 0.007 parts by weight of tetra-n-butoxytitanium, 0.007 parts by weight of trimethyl phosphate, and 0.01 parts by weight of magnesium acetate tetrahydrate were added and stirred for 5 minutes. Next, 0.01 parts by weight of tetrabutylammonium methanesulfonate was added and stirred for 5 minutes. Subsequently, the pressure in the polymerization reactor was gradually reduced to 0.13 kPa or less over 35 minutes, and the temperature was gradually increased to 279°C. The polymerization reaction was carried out until the intrinsic viscosity of the polyester resin composition reached 0.625. The polycondensation reactor was then returned to normal pressure using nitrogen gas, and the polyester resin composition was extruded into cold water in the form of a strand through a die and pelletized into cylindrical pellets using an extrusion cutter to obtain a polyester resin composition. A polyester film was also obtained in the same manner as in Example 1. The obtained polyester resin composition contained the amounts of sulfur, phosphorus, and manganese shown in Table 3. The results are shown in Table 4. Because it contained a large amount of magnesium, the color b value and coarse foreign matter were unacceptable.

[0081] (Comparative Example 10) To a mixture of 100 parts by weight of dimethyl terephthalate and 70 parts by weight of ethylene glycol, 0.038 parts by weight of manganese acetate tetrahydrate was added, and an ester exchange reaction was carried out while gradually increasing the temperature from 150°C to 240°C. When the reaction temperature reached 170°C, 0.010 parts by weight of diantimony trioxide was added. Subsequently, an ester exchange reaction was carried out, and after completion of the ester exchange reaction, trimethyl phosphate was added in ethylene glycol at 135°C for 5 hours at 1.1-1.6 kg / cm. 2 The heated solution (0.049 parts by weight in terms of trimethyl phosphate) was added under pressure of 1000 kJ / min, and the reaction product was then transferred to a polymerization reactor, heated to 290°C, and subjected to a polycondensation reaction under a high vacuum of 0.2 mmHg or less to obtain polyester chips with an intrinsic viscosity of 0.625.

[0082] Next, 100 parts by weight of the polyester chips obtained by the above method and 0.031 parts by weight of tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate were fed into a co-rotating twin-screw extruder (Toshiba Kikai Co., Ltd. TEM-35B), and the extrusion temperature was 300°C, the shear rate was 150 s -1 The mixture was kneaded under conditions of a residence time of 3.5 minutes, discharged, cooled with water, and pelletized to obtain a polyester resin composition. Also, a polyester film was obtained in the same manner as in Example 1. The resulting polyester resin composition contained the amounts of sulfur, phosphorus, and manganese listed in Table 3. However, because sulfonic acid compounds were copolymerized components, the sulfonic acid compounds could not be detected by method (13). The results are shown in Table 4. Because the resulting polyester resin composition contained large amounts of phosphorus and manganese, it failed the color b value, heat resistance, and coarse foreign matter tests.

[0083] [Table 3]

[0084] [Table 4]

[0085] Example 14 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that 0.0007 parts by weight of tetra-n-butyl titanate was added as an ethylene glycol solution instead of adding diantimony trioxide, resulting in the titanium element content shown in Table 5. The results are shown in Table 6. The color tone b value of the obtained polyester resin composition was 8.3, and the melt resistivity was 2.3 × 10 6 Ω·cm, main chain scission rate of heat resistance index is 0.34%, coarse foreign matter of 1μm or more is 115 pieces / 0.1mm 2 The solution haze was 0.3%, which was excellent. The polyester film obtained had good film-forming properties and an excellent total light transmittance of 92.5%.

[0086] (Examples 15 and 16) A polyester resin composition and a polyester film were obtained in the same manner as in Example 14, except that the amount of tetra-n-butyl titanate added was changed to obtain the titanium element content shown in Table 5. The results are shown in Table 6. The polyester resin composition and polyester film obtained in Example 15 had excellent or good physical properties in all evaluations. The polyester resin composition obtained in Example 16 had an increased color tone b value but was still within the acceptable range, and the other evaluations were excellent or good. The obtained polyester film also had excellent or good physical properties.

[0087] Example 17 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that 0.0015 parts by weight of germanium dioxide was added as an ethylene glycol solution instead of adding diantimony trioxide, resulting in the germanium content shown in Table 5. The results are shown in Table 6. The obtained polyester resin composition and polyester film had excellent or good physical properties in all evaluations.

[0088] (Examples 18 and 19) A polyester resin composition and a polyester film were obtained in the same manner as in Example 17, except that the amount of germanium dioxide added was changed to the germanium content shown in Table 5. The results are shown in Table 6. The polyester resin compositions and polyester films obtained in Examples 18 and 19 had excellent or good physical properties in all evaluations.

[0089] Examples 20 to 22 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that sodium p-toluenesulfonate and tetrabutylphosphonium hydroxide were added as an ethylene glycol solution instead of adding tetrabutylphosphonium p-toluenesulfonate, and the sulfur and phosphorus contents were as shown in Table 5. The results are shown in Table 6. The color tone b value of the polyester resin composition obtained in Example 20 was 8.3, and the melt resistivity was 2.2 × 10 6 Ω·cm, main chain scission rate of heat resistance index is 0.33%, coarse foreign matter of 1μm or more is 115 pieces / 0.1mm 2 The solution haze was 0.3%, which was excellent. The resulting polyester film had good film-forming properties and an excellent total light transmittance of 92.7%. The polyester resin composition obtained in Example 21 had an increased melt resistivity compared to the polyester resin composition of Example 20, but was still within the acceptable range. In addition, the film-forming properties of the polyester film also passed the test. The polyester resin composition obtained in Example 22 had a larger color tone b value than the polyester resin composition of Example 20, but was still within the acceptable range. The polyester film obtained was evaluated as excellent or good.

[0090] (Examples 23 to 27) A polyester resin composition and a polyester film were obtained in the same manner as in Example 20, except that a sulfur compound shown in Table 5 was added instead of sodium p-toluenesulfonate. The results are shown in Table 6. The polyester resin compositions and polyester films obtained in Examples 23 and 27 had excellent or good physical properties in all evaluations. The polyester resin compositions obtained in Examples 24 to 26 had increased melt resistivities but were still within the acceptable range compared to the polyester resin composition of Example 20. The polyester films obtained were evaluated as excellent or good.

[0091] Example 28 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that tetrabutylphosphonium dodecylsulfonate was added as an ethylene glycol solution instead of tetrabutylphosphonium p-toluenesulfonate, and the sulfur and phosphorus contents were as shown in Table 5. The results are shown in Table 6. The resulting polyester resin composition had increased melt resistivity, solution haze, and coarse foreign matter compared to the polyester resin composition of Example 1, but all of these were within acceptable ranges. In addition, the total light transmittance of the resulting polyester film was low but within acceptable ranges.

[0092] [Table 5]

[0093] [Table 6]

[0094] (Examples 29 and 30) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that after adding diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate, agglomerated silica particles having a volume average particle size of 2.5 μm were added as an ethylene glycol slurry so as to obtain the content shown in Table 7. The polyester resin compositions obtained in Examples 29 and 30 all had good color tone b value, melt resistivity, and heat resistance, and the solution haze and coarse foreign matter were within acceptable ranges. The polyester films obtained all had good film-forming properties and total light transmittance within acceptable ranges.

[0095] Example 31 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that tetra-n-butoxytitanate and tetrabutylphosphonium p-toluenesulfonate were added, and then agglomerated silica particles having a volume average particle size of 2.5 μm were added as an ethylene glycol slurry, and the contents of sulfur element, phosphorus element, titanium element, and particles were set as shown in Table 8. The obtained polyester resin composition had good color tone b value, melt resistivity, and heat resistance, and the solution haze and coarse foreign matter were within acceptable ranges. The obtained polyester film also had good film-forming properties and a total light transmittance within acceptable ranges.

[0096] (Comparative Example 11) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that 105 parts by weight of the esterification reaction product (corresponding to 100 parts by weight of PET) obtained by the esterification reaction was charged into a polymerization apparatus, and then 0.0084 parts by weight of diantimony trioxide and 0.090 parts by weight of calcium acetate were added as ethylene glycol solutions, followed by 0.070 parts by weight of triethylphosphonoacetate as an ethylene glycol solution, and finally agglomerated silica particles having a volume average particle size of 2.5 μm were added, and the pressure inside the polymerization reaction tank was gradually reduced. The resulting polyester resin composition contained the amounts of phosphorus, calcium, antimony, and particles shown in Table 7. The obtained polyester resin composition had acceptable melt resistivity and heat resistance, but because it contained a large amount of calcium element, it failed the evaluations of color tone b value, solution haze, and large foreign matter. Furthermore, the obtained polyester film had no problems with film formation, but its total light transmittance was low and its transparency was insufficient.

[0097] (Examples 32 and 33) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that after adding diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate, colloidal silica particles having a volume average particle size of 0.06 μm were added as an ethylene glycol slurry so as to obtain the contents shown in Table 7. The polyester resin composition obtained in Example 32 was excellent in color tone b value, melt resistivity, heat resistance, and coarse foreign matter content, and the solution haze was within the acceptable range. The obtained polyester film also had good film-forming properties and a total light transmittance within the acceptable range. The polyester resin composition obtained in Example 33 was excellent in color tone b value, melt resistivity, heat resistance, coarse foreign matter, and solution haze. The obtained polyester film was also excellent in film formability and total light transmittance.

[0098] Example 34 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that tetra-n-butoxytitanate and tetrabutylphosphonium p-toluenesulfonate were added, and then colloidal silica particles having a volume average particle size of 0.06 μm were added as an ethylene glycol slurry, and the contents of sulfur element, phosphorus element, titanium element, and particles were set as shown in Table 8. The obtained polyester resin composition had good color tone b value, melt resistivity, heat resistance, and coarse foreign matter content, and the solution haze was within the acceptable range. The obtained polyester film also had good film-forming properties and a total light transmittance within the acceptable range.

[0099] (Examples 35 and 36) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that after adding diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate, alumina particles having a volume average particle size of 0.015 μm were added as an ethylene glycol slurry so as to obtain the content shown in Table 7. The polyester resin composition obtained in Example 35 had good melt resistivity and heat resistance, and the color tone b value, solution haze, and coarse foreign matter were all within the acceptable ranges. The polyester film obtained also had good film-forming properties and a total light transmittance within the acceptable ranges. The polyester resin composition obtained in Example 36 was excellent in all the property evaluations, and the obtained polyester film was excellent in both film formability and total light transmittance.

[0100] Example 37 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that tetra-n-butoxytitanate and tetrabutylphosphonium p-toluenesulfonate were added, and then alumina particles having a volume average particle size of 0.015 μm were added as an ethylene glycol slurry, and the contents of sulfur element, phosphorus element, titanium element, and particles were set as shown in Table 8. The polyester resin composition obtained had good melt resistivity and heat resistance, and the color tone b value, solution haze, and coarse foreign matter were all within acceptable ranges. The polyester film obtained also had good film-forming properties and a total light transmittance within acceptable ranges.

[0101] (Examples 38 and 39) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that after adding diantimony trioxide and tetrabutylphosphonium p-toluenesulfonate, crosslinked polystyrene particles having a volume average particle size of 0.32 μm were added as an ethylene glycol slurry so as to obtain the contents shown in Table 7. The polyester resin composition obtained in Example 38 had good melt resistivity and heat resistance, and the color tone b value, solution haze, and coarse foreign matter were all within the acceptable ranges. The polyester film obtained also had good film-forming properties and a total light transmittance within the acceptable ranges. The polyester resin composition obtained in Example 39 was excellent in all the property evaluations, and the obtained polyester film was excellent in both film formability and total light transmittance.

[0102] Example 40 A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that tetra-n-butoxytitanate and tetrabutylphosphonium p-toluenesulfonate were added, and then crosslinked polystyrene particles having a volume average particle size of 0.32 μm were added as an ethylene glycol slurry, and the contents of sulfur element, phosphorus element, titanium element, and particles were set as shown in Table 8. The polyester resin composition obtained had good melt resistivity and heat resistance, and the color tone b value, solution haze, and coarse foreign matter were all within acceptable ranges. The polyester film obtained also had good film-forming properties and a total light transmittance within acceptable ranges.

[0103] (Comparative Example 12) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that instead of adding tetrabutylphosphonium p-toluenesulfonate, the copolymerization component tetrabutylphosphonium 3,5-dicarboxybenzenesulfonate was added, and the sulfur and phosphorus contents were as shown in Table 7. Because the sulfonic acid compound was a copolymerization component, the sulfonic acid compound in the polyester resin composition could not be detected by method (13). The results are shown in Table 8. The resulting polyester resin composition contained a large amount of sulfur element, and therefore failed in the color tone b value. Furthermore, compared with the polyester resin composition of Example 1, the addition of a large amount of the sulfonic acid compound, which is a copolymerization component, resulted in a large amount of coarse foreign matter, and the melting point was also low, resulting in a failure.

[0104] (Comparative Example 13) A polyester resin composition and a polyester film were obtained in the same manner as in Example 1, except that the sulfur element and phosphorus element contents were set as shown in Table 7. The results are shown in Table 8. The resulting polyester resin composition contained a large amount of sulfur element, and therefore failed to pass the color tone b value. Furthermore, the solution haze and coarse foreign matter increased compared to the polyester resin composition of Example 1, but were still within the acceptable range. Although a large amount of sulfonic acid compound was added, it was not a copolymerization component, and therefore the melting point was within the acceptable range, similar to that of the polyester resin composition of Example 1. The total light transmittance of the resulting polyester film was low, but within the acceptable range.

[0105] (Comparative Example 14) A polyester resin composition was obtained in the same manner as in Example 1, except that sodium dodecylbenzenesulfonate was added instead of tetrabutylphosphonium p-toluenesulfonate, and the sulfur element content was set as shown in Table 1. The resulting polyester resin composition was unacceptable due to its high melt resistivity. In addition, there was a problem with adhesion to the casting drum during polyester film production, making it impossible to obtain a polyester film.

[0106] [Table 7]

[0107] [Table 8]

Claims

1. containing sulfur element and phosphorus element, the sulfur element content being 2 to 20 ppm by weight, the phosphorus element content being 2 to 20 ppm by weight, and the total content of calcium element, magnesium element and manganese element being 5 ppm by weight or less, relative to the weight of the polyester resin composition; The polyester contains a sulfonic acid compound represented by the following chemical formula (1) in an amount of 1 to 12 mmol% based on the acid component of the polyester, A polyester resin composition comprising a phosphorus compound selected from at least one of phosphoric acid, trimethyl phosphate, ethyl diethyl phosphonoacetate, phosphorous acid, alkali metal phosphates, and salts having a quaternary phosphonium cation. 【Chemistry 1】 (A is an aryl group having 6 to 7 carbon atoms. X is hydrogen, an alkali metal, a quaternary phosphonium cation, or a quaternary ammonium cation.)

2. 2. The polyester resin composition according to claim 1, further comprising titanium or germanium.

3. 3. The polyester resin composition according to claim 1, wherein the content of titanium element is 0.1 to 20 ppm by weight based on the polyester resin composition.

4. 3. The polyester resin composition according to claim 1, wherein the content of germanium element is 5 to 150 ppm by weight based on the polyester resin composition.

5. 2. The polyester resin composition according to claim 1, wherein the content of the inorganic particles is 0.001 to 6.5% by weight based on the polyester resin composition.

6. 6. The polyester resin composition according to claim 5, wherein the inorganic particles are silica particles.

7. 7. The polyester resin composition according to claim 6, wherein the silica particles are aggregated silica having a volume average particle diameter of 1.0 to 5.0 μm.

8. 7. The polyester resin composition according to claim 6, wherein the silica particles are colloidal silica having a volume average particle diameter of 0.05 to 0.5 μm.

9. 6. The polyester resin composition according to claim 5, wherein the inorganic particles are alumina particles having a volume average particle size of 0.01 to 1.0 μm.

10. 2. The polyester resin composition according to claim 1, wherein the content of the organic particles is 0.001 to 5.0% by weight based on the polyester resin composition.

11. 11. The polyester resin composition according to claim 10, wherein the organic particles are crosslinked polystyrene particles having a volume average particle size of 0.1 to 1.5 μm.

12. The polyester resin composition according to any one of claims 1 to 11, which is used for a polyester film for release purposes.

13. The polyester resin composition according to any one of claims 1 to 11, which is used for a polyester film for optical applications.

14. A polyester film using the polyester resin composition according to any one of claims 1 to 13.

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