Method for producing polyester resin composition

Abstract

Provided is a method for producing a polyester resin composition, whereby it becomes possible to reduce catalyst cost when a polymerization catalyst comprising an aluminum compound and a phosphorus compound is used and to reduce foreign matters in the polyester resin composition. The method for producing a polyester resin composition is characterized by comprising a step for mixing a base polyester resin (A) comprising an aluminum compound and a phosphorus compound and satisfying items (1) to (3) with a master batch (B) comprising an anti-blocking agent.　(1) The content of element aluminum in the base polyester resin (A) is 9 to 19 ppm by mass; (2) the content of element phosphorus in the base polyester resin (A) is 13 to 31 ppm by mass; and (3) the molar ratio of element phosphorus to element aluminum in the base polyester resin (A) is 1.32 to 1.80, inclusive.

Description

[Technical Field]

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

[0002] Polyester resins, such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and polyethylene naphthalate (PEN), have excellent mechanical and chemical properties, and are used in a wide range of fields depending on the properties of each polyester resin, such as fibers for clothing and industrial materials, various films and sheets for packaging and industrial use, and molded products such as bottles and engineering plastics.

[0003] A typical polyester resin, whose main components are units derived from aromatic dicarboxylic acids and alkylene glycols, is industrially produced, for example, in the case of polyethylene terephthalate (PET), by esterifying or transesterifying terephthalic acid or dimethyl terephthalate with ethylene glycol to produce bis(2-hydroxyethyl) terephthalate, which is then polycondensed at high temperature in a vacuum using a catalyst.

[0004] Antimony compounds or germanium compounds have traditionally been widely used as polyester polymerization catalysts for the polymerization of polyester resins. Antimony trioxide, an example of an antimony compound, is an inexpensive catalyst with excellent catalytic activity. However, when used as the main component, i.e., in an amount sufficient to achieve a practical polymerization rate, metallic antimony precipitates during polymerization, causing blackening and foreign matter in the polyester resin and resulting in surface defects in the film. Furthermore, when used as a raw material for hollow molded products, it is difficult to obtain hollow molded products with excellent transparency. For these reasons, there is a demand for polyester resins that do not contain any antimony compounds or do not contain antimony compounds as the main catalyst component.

[0005] Germanium compounds have already been put to practical use as catalysts that have excellent catalytic activity and produce polyester resins that do not have the above-mentioned problems, other than antimony compounds. However, germanium compounds have the problems of being very expensive and being easily distilled out of the reaction system during polymerization, which changes the catalyst concentration in the reaction system and makes it difficult to control the polymerization, making their use as a main catalyst component problematic.

[0006] Studies are also being conducted on polymerization catalysts that can replace antimony- or germanium-based catalysts. Titanium compounds, such as tetraalkoxy titanates, have already been proposed, but polyester resins produced using titanium compounds are susceptible to thermal degradation during melt molding and suffer from significant coloration.

[0007] In light of the above, there is a need for a polymerization catalyst that contains a metal component other than antimony, germanium, and titanium as the main metal component of the catalyst, and that can give polyester resins that have excellent catalytic activity, excellent color tone and thermal stability, and excellent transparency in molded products.

[0008] For example, Patent Documents 1 and 2 disclose a catalyst composed of an aluminum compound and a phosphorus compound as a novel polymerization catalyst. However, Patent Documents 1 and 2 have problems in that the catalyst loading is large and the cost of the phosphorus compound used is high, resulting in high catalyst costs required for polymerization and low polymerization activity.

[0009] Furthermore, when a polyester film is produced using a polyester resin, it is generally necessary to form surface protrusions on the surface of the resulting polyester film using an antiblocking agent, thereby improving the handling properties of the film, such as slipperiness, running properties, abrasion resistance, and winding properties.

[0010] On the other hand, Patent Document 3 discloses a polyester composition for film containing a polyester resin containing no inorganic particles and a polyester composition for masterbatch containing inorganic particles and produced using a catalyst comprising an aluminum compound and a phosphorus compound. This technology also has the problem of high catalyst costs required for polymerization because the amount of catalyst added, particularly the amount of phosphorus compound added, is large and the cost of the phosphorus compound used is also high. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] International Publication No. 2007 / 032325 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-169432 [Patent Document 3] International Publication No. 2013 / 146524 Summary of the Invention [Problem to be solved by the invention]

[0012] The present invention has been made to solve the problems of the prior art, and its object is to produce a polyester resin composition using a base polyester resin, which has high polymerization activity, reduced catalyst costs, and little foreign matter, despite the use of a polymerization catalyst comprising an aluminum compound and a phosphorus compound. [Means for solving the problem]

[0013] As a result of extensive research to solve the above problems, the present inventors discovered that the object can be achieved by reducing the amount of aluminum element contained in the base polyester resin and adjusting the molar ratio of phosphorus element to aluminum element within an appropriate range, and thus arrived at the present invention. When a polymerization catalyst such as an antimony compound or a germanium compound is used in polyester polymerization, the polymerization activity is generally proportional to the amount of catalyst added. However, when a polymerization catalyst is composed of an aluminum compound and a phosphorus compound, the polymerization activity is affected by the complex formation reaction between the aluminum compound and the phosphorus compound, so the relationship between the polymerization activity and the amount of catalyst added cannot be simplified.

[0014] Therefore, the present inventors analyzed the factors that govern the catalytic activity of a polymerization catalyst composed of an aluminum compound and a phosphorus compound, and found that by reducing the amount of aluminum element in the base polyester resin and adjusting the molar ratio of phosphorus element to aluminum element within an appropriate range, it is possible to suppress an increase in the amount of aluminum-based foreign matter while also improving polymerization activity, while keeping catalyst costs down, and completed the present invention.

[0015] That is, the present invention comprises the following configurations. [1] A method for producing a polyester resin composition, comprising a step of mixing a base polyester resin (A) containing an aluminum compound and a phosphorus compound and satisfying the following (1) to (3) with a masterbatch (B) containing an antiblocking agent: (1) The aluminum element content in the base polyester resin (A) is 9 to 19 ppm by mass. (2) The content of phosphorus element in the base polyester resin (A) is 13 to 31 mass ppm. (3) the molar ratio of phosphorus to aluminum in the base polyester resin (A) is 1.32 or more and 1.80 or less; [2] The method for producing a polyester resin composition according to [1], wherein the masterbatch (B) contains insoluble particles that are insoluble in the base polyester resin (A), the insoluble particles have a volume average particle diameter of 0.5 to 3.0 μm, and the content of the insoluble particles is 0.5 to 20 mass %. [3] The method for producing a polyester resin composition according to [1] or [2], further comprising mixing a masterbatch (C) containing an electrostatic adhesion imparting agent. [4] The method for producing a polyester resin composition according to [3], wherein the masterbatch (C) is a polyester resin containing a magnesium compound, an alkali metal compound, and a phosphorus compound, and the masterbatch (C) contains 400 to 2700 ppm by mass of magnesium element, 40 to 270 ppm by mass of alkali metal element, and 200 to 1700 ppm by mass of phosphorus element. [5] The method for producing the polyester resin composition according to [1] or [2], wherein a masterbatch (D) containing an antiblocking agent and an electrostatic adhesion imparting agent is mixed with the base polyester resin (A) instead of the masterbatch (B). [6] The method for producing a polyester resin composition according to [5], wherein the masterbatch (D) contains insoluble particles that are insoluble in the base polyester resin (A), the insoluble particles having a volume average particle diameter of 0.5 to 3.0 μm and a content of the insoluble particles of 0.5 to 20 mass %, and further the masterbatch (D) contains 400 to 2700 mass ppm of magnesium element, 40 to 270 mass ppm of alkali metal element, and 200 to 1700 mass ppm of phosphorus element. [7] The method for producing a polyester resin composition according to [4] or [6] above, wherein the alkali metal contained in the masterbatch (C) or the masterbatch (D) is potassium. [8] The method for producing a polyester resin composition according to any one of [4], [6], and [7], wherein the phosphorus compound contained in the masterbatch (C) or the masterbatch (D) is a trialkyl phosphate, and at least one of the alkyl groups of the trialkyl phosphate has 2 to 4 carbon atoms. [9] The method for producing a polyester resin composition according to [8], wherein the phosphorus compound contained in the masterbatch (C) or the masterbatch (D) is triethyl phosphate.

[10] The melt resistivity of the masterbatch (C) or the masterbatch (D) is 0.005 × 10 8 ~0.05×10 8 The method for producing a polyester resin composition according to any one of [3] to [9] above, wherein the resistivity is Ω·cm.

[11] The method for producing a polyester resin composition according to any one of [3] to

[10] , wherein the masterbatch (C) or the masterbatch (D) is a polyester having a dicarboxylic acid component and a glycol component as constituent components, and satisfies the following (4), when the amount of magnesium element, the amount of alkali metal element, and the amount of phosphorus element relative to the dicarboxylic acid component are m (mol %), k (mol %), and p (mol %): (4) 2≦(m+k / 2) / p≦3.5

[12] The method for producing a polyester resin composition according to any one of [1] to

[11] , wherein the phosphorus compound contained in the base polyester resin (A) has a phosphorus element and a phenol structure in the same molecule.

[13] The method for producing a polyester resin composition according to any one of [1] to

[12] above, wherein the content of aluminum element corresponding to aluminum-based foreign matter in the base polyester resin (A) is 3000 mass ppm or less.

[14] The method for producing a polyester resin composition according to any one of [1] to

[13] above, wherein the base polyester resin (A) has an intrinsic viscosity (IV) of 0.56 dl / g or more.

[15] A method for producing the base polyester resin (A) according to any one of [1] to

[14] , comprising a first step of synthesizing a polyester or an oligomer thereof as a polycondensation product as an intermediate, and a second step of further polycondensing the intermediate, wherein after the first step and before the second step, a solution A1 in which an aluminum compound is dissolved and a solution B1 in which a phosphorus compound is dissolved are added to the intermediate, and the amounts of the solution A1 and the solution B1 added satisfy the following (5) to (7): (5) The amount of aluminum element added to the base polyester resin (A) produced is 9 to 19 ppm by mass. (6) The amount of phosphorus added to the base polyester resin (A) to be produced is 18 to 38 mass ppm. (7) The molar ratio of the amount of added phosphorus element in (6) to the amount of added aluminum element in (5) is 1.50 or more and 2.30 or less.

[16] The method for producing a polyester resin composition according to

[15] , wherein the base polyester resin (A) is produced by a batch polymerization method.

[17] The method for producing a polyester resin composition according to

[15] , wherein the base polyester resin (A) is produced by a continuous polymerization method, and the solution A1 and the solution B1 are added to a final esterification reaction tank or a transfer line between the final esterification reaction tank and a first polymerization reaction tank.

[18] The method for producing a polyester resin composition according to any one of

[15] to

[17] , wherein the solution A1 is a glycol solution, and the maximum absorption wavelength of the solution A1 is 562.0 to 572.0 nm.

[19] The method for producing a polyester resin composition according to

[18] , wherein the solution B1 is a glycol solution, and the maximum absorption wavelength of the solution B1 is 458.0 to 465.0 nm.

[20] The method for producing a polyester resin composition according to any one of

[15] to

[19] , wherein the solution A1 and the solution B1 are glycol solutions, and the maximum absorption wavelength of a mixture of the glycol solution A1 and the glycol solution B1 is 559.5 to 560.8 nm. [Effects of the Invention]

[0016] The polyester resin composition produced by the production method of the present invention uses a polymerization catalyst comprising an aluminum compound and a phosphorus compound, but by using a base polyester resin that keeps catalyst costs low and reduces catalyst-derived foreign matter contained in the polyester resin, the cost of producing the polyester resin composition can be reduced and the quality of the polyester resin composition can be improved. Furthermore, by adjusting the acidity or basicity of the aluminum compound solution, phosphorus compound solution, or mixture thereof added as a catalyst to fall within a preferred range (by adjusting the maximum absorption wavelength of the solution or mixture within a preferred range), the amount of aluminum-based foreign matter in the base polyester resin can be further reduced. Furthermore, since the polyester resin composition obtained by the production method of the present invention can be obtained at low cost and has high quality, the production cost of the polyester film obtained by forming the polyester resin composition into a film can be reduced and the quality of the polyester film can be improved. Furthermore, since the polyester film has excellent running properties, abrasion resistance, optical properties, etc., it can be used in a wide range of applications such as packaging films and industrial films. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 2 is a correlation diagram between the residual molar ratio of phosphorus element to aluminum element, the amount of aluminum-based foreign matter, and the polymerization time, determined from the results of Examples and Comparative Examples. [Figure 2] FIG. 1 is a correlation diagram between the maximum absorption wavelength of a mixed solution of a phosphorus-containing ethylene glycol solution and an aluminum-containing ethylene glycol solution and the amount of aluminum-based foreign matter and polymerization time, determined from the results of Examples and Comparative Examples. [Figure 3] FIG. 1 is a correlation diagram between the maximum absorption wavelength and the back pressure increase coefficient of a mixed solution of an aluminum-containing ethylene glycol solution and a phosphorus-containing ethylene glycol solution, determined from the results of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in detail below.

[0019] The method for producing a polyester resin composition of the present invention includes a step of mixing a base polyester resin (A) with a masterbatch (B) containing an antiblocking agent. Hereinafter, the base polyester resin (A) will be simply referred to as "polyester resin (A)," and the masterbatch (B) containing an antiblocking agent will be referred to as "antiblocking agent-containing masterbatch (B)" or "masterbatch (B)."

[0020] [Polyester resin (A)] The polyester resin (A) contains an aluminum compound and a phosphorus compound, and satisfies the following (1) to (3): (1) The aluminum element content in the polyester resin (A) is 9 to 19 ppm by mass. (2) The content of phosphorus element in the polyester resin (A) is 13 to 31 mass ppm. (3) The molar ratio of phosphorus to aluminum in the polyester resin (A) is 1.32 or more and 1.80 or less. In this specification, ppm by mass is 10 -4 The percentages represent mass %.

[0021] The polyester resin (A) includes a polyester resin composed of at least one selected from polycarboxylic acids and their ester-forming derivatives, and at least one selected from polyhydric alcohols and their ester-forming derivatives.

[0022] In the polyester resin (A), the main polycarboxylic acid component is preferably a dicarboxylic acid, and the main polyhydric alcohol component is preferably a glycol.

[0023] The polyester resin (A) whose main polycarboxylic acid component is a dicarboxylic acid is preferably a polyester resin containing 70 mol% or more of dicarboxylic acid relative to the total polycarboxylic acid components, more preferably a polyester resin containing 80 mol% or more, and even more preferably a polyester resin containing 90 mol% or more. When two or more dicarboxylic acids are used, the total content thereof is preferably within the above range.

[0024] Examples of dicarboxylic acids include saturated aliphatic dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, decanedicarboxylic acid, dodecanedicarboxylic acid, tetradecanedicarboxylic acid, hexadecanedicarboxylic acid, 1,3-cyclobutanedicarboxylic acid, 1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 2,5-norbornanedicarboxylic acid, and dimer acid, and ester-forming derivatives thereof; and unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, and itaconic acid. or ester-forming derivatives thereof; aromatic dicarboxylic acids exemplified by orthophthalic acid, isophthalic acid, terephthalic acid, 5-(alkali metal)sulfoisophthalic acid, diphenic acid, 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 4,4'-biphenylsulfonedicarboxylic acid, 4,4'-biphenyletherdicarboxylic acid, 1,2-bis(phenoxy)ethane-p,p'-dicarboxylic acid, pamoic acid, anthracenedicarboxylic acid, and the like, or ester-forming derivatives thereof;

[0025] More preferably, the main polycarboxylic acid component is terephthalic acid or its ester-forming derivative, or naphthalenedicarboxylic acid or its ester-forming derivative. Examples of naphthalenedicarboxylic acid or its ester-forming derivative include 1,3-naphthalenedicarboxylic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, or their ester-forming derivatives.

[0026] The polyester resin (A) whose main polycarboxylic acid component is terephthalic acid or its ester-forming derivative or naphthalenedicarboxylic acid or its ester-forming derivative is preferably a polyester resin containing terephthalic acid or its ester-forming derivative and naphthalenedicarboxylic acid or its ester-forming derivative in a total amount of 70 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more of the total polycarboxylic acid components.

[0027] Terephthalic acid, 2,6-naphthalenedicarboxylic acid, or an ester-forming derivative thereof is particularly preferred. If necessary, other dicarboxylic acids may be used as constituent components.

[0028] As polycarboxylic acids other than these dicarboxylic acids, trivalent or higher polycarboxylic acids or hydroxycarboxylic acids may be used in small amounts, with trivalent or tetravalent polycarboxylic acids being preferred. Examples of polycarboxylic acids include ethanetricarboxylic acid, propanetricarboxylic acid, butanetetracarboxylic acid, pyromellitic acid, trimellitic acid, trimesic acid, 3,4,3',4'-biphenyltetracarboxylic acid, and ester-forming derivatives thereof. The trivalent or higher polycarboxylic acid is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less, of the total polycarboxylic acid components. When two or more trivalent or higher polycarboxylic acids are used, the total amount is preferably within the above range.

[0029] Examples of hydroxycarboxylic acids include lactic acid, citric acid, malic acid, tartaric acid, hydroxyacetic acid, 3-hydroxybutyric acid, p-hydroxybenzoic acid, p-(2-hydroxyethoxy)benzoic acid, 4-hydroxycyclohexanecarboxylic acid, and ester-forming derivatives thereof. The hydroxycarboxylic acid content of the total polycarboxylic acid components is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less. When two or more hydroxycarboxylic acids are used, the total content is preferably within the above range.

[0030] Examples of the ester-forming derivatives of polycarboxylic acids or hydroxycarboxylic acids include alkyl esters, acid chlorides, and acid anhydrides thereof.

[0031] The polyester resin (A) preferably contains a glycol as the main polyhydric alcohol component.

[0032] The polyester resin (A) whose main polyhydric alcohol component is glycol is preferably a polyester resin containing 70 mol % or more of glycol based on the total polyhydric alcohol components, more preferably a polyester resin containing 80 mol % or more, and even more preferably a polyester resin containing 90 mol % or more. When two or more glycols are used, the total content thereof is preferably within the above range.

[0033] Examples of glycols include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, diethylene glycol, triethylene glycol, 1,2-butylene glycol, 1,3-butylene glycol, 2,3-butylene glycol, 1,4-butylene glycol, 1,5-pentanediol, neopentyl glycol, 1,6-hexanediol, 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,4-cyclohexanediethanol, 1,10-decamethylene glycol, and 1,12-dodecanediol. aliphatic glycols exemplified by polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol, and the like; aromatic glycols exemplified by hydroquinone, 4,4'-dihydroxybisphenol, 1,4-bis(β-hydroxyethoxy)benzene, 1,4-bis(β-hydroxyethoxyphenyl)sulfone, bis(p-hydroxyphenyl)ether, bis(p-hydroxyphenyl)sulfone, bis(p-hydroxyphenyl)methane, 1,2-bis(p-hydroxyphenyl)ethane, bisphenol A, bisphenol C, 2,5-naphthalenediol, glycols in which ethylene oxide is added to these glycols, and the like.

[0034] Among these glycols, alkylene glycols are preferred, and more preferably ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, or 1,4-cyclohexanedimethanol. The alkylene glycols may contain a substituent or an alicyclic structure in the molecular chain, and two or more types may be used simultaneously.

[0035] A small amount of a trihydric or higher polyhydric alcohol may be used in combination with these glycols, and a tri- or tetrahydric polyhydric alcohol is preferred. Examples of trihydric or higher polyhydric alcohols include trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, glycerol, and hexanetriol.

[0036] The trihydric or higher polyhydric alcohol is preferably 20 mol% or less, more preferably 10 mol% or less, and even more preferably 5 mol% or less of the total polyhydric alcohol component. When two or more trihydric or higher polyhydric alcohols are used, the total amount thereof is preferably within the above range.

[0037] The use of a cyclic ester in combination is also permitted. Examples of cyclic esters include ε-caprolactone, β-propiolactone, β-methyl-β-propiolactone, δ-valerolactone, glycolide, and lactide. Examples of ester-forming derivatives of polyhydric alcohols include esters of polyhydric alcohols with lower aliphatic carboxylic acids such as acetic acid.

[0038] The cyclic ester is preferably 20 mol % or less, more preferably 10 mol % or less, and even more preferably 5 mol % or less, based on the total of all polycarboxylic acid components and all polyhydric alcohol components. When two or more cyclic esters are used, the total amount thereof is preferably within the above range.

[0039] The polyester resin (A) is preferably a polymer consisting of only one monomer selected from ethylene terephthalate, butylene terephthalate, propylene terephthalate, 1,4-cyclohexanedimethylene terephthalate, ethylene naphthalate, butylene naphthalate, or propylene naphthalate, or a copolymer consisting of two or more of the above monomers, and the polyester resin (A) is more preferably polyethylene terephthalate or a copolymer consisting of ethylene terephthalate and at least one of the above monomers other than ethylene terephthalate, and particularly preferably polyethylene terephthalate. The copolymer consisting of ethylene terephthalate and at least one of the above monomers other than ethylene terephthalate preferably contains 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more of a component derived from ethylene terephthalate monomer.

[0040] <Polymerization catalyst> The polyester resin (A) contains catalytic amounts of an aluminum compound-derived component and a phosphorus compound-derived component, i.e., the polyester resin (A) is produced using a polymerization catalyst consisting of an aluminum compound and a phosphorus compound.

[0041] <Aluminum compounds> The aluminum compound constituting the polymerization catalyst is not limited as long as it is soluble in a solvent, and known aluminum compounds can be used without limitation. Examples of aluminum compounds include carboxylates such as aluminum formate, aluminum acetate, basic aluminum acetate, aluminum propionate, aluminum oxalate, aluminum acrylate, aluminum laurate, aluminum stearate, aluminum benzoate, aluminum trichloroacetate, aluminum lactate, aluminum citrate, aluminum tartrate, and aluminum salicylate; inorganic acid salts such as aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, aluminum nitrate, aluminum sulfate, aluminum carbonate, aluminum phosphate, and aluminum phosphonate; aluminum methoxide, aluminum ethoxide, aluminum n-propoxide, and aluminum aluminum alkoxides such as aluminum isopropoxide, aluminum n-butoxide, and aluminum t-butoxide; chelate compounds such as aluminum acetylacetonate, aluminum ethyl acetoacetate, and aluminum ethyl acetoacetate di-isopropoxide; organoaluminum compounds such as trimethylaluminum and triethylaluminum and their partial hydrolysates; reaction products of aluminum alkoxides or aluminum chelate compounds with hydroxycarboxylic acids; aluminum oxide, ultrafine aluminum oxide, aluminum silicate, and composite oxides of aluminum with titanium, silicon, zirconium, alkali metals, alkaline earth metals, etc. Of these, at least one selected from carboxylates, inorganic acid salts, and chelate compounds is preferred, and among these, at least one selected from aluminum acetate, basic aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, and aluminum acetylacetonate is more preferred, at least one selected from aluminum acetate, basic aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxide chloride, and aluminum acetylacetonate is even more preferred, at least one selected from aluminum acetate and basic aluminum acetate is particularly preferred, and basic aluminum acetate is most preferred.

[0042] The aluminum compound is preferably an aluminum compound that is soluble in a solvent such as water or glycol. Solvents that can be used in the present invention include water and alkylene glycols. Examples of alkylene glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, trimethylene glycol, ditrimethylene glycol, tetramethylene glycol, ditetramethylene glycol, and neopentyl glycol. Preferably, the solvent is at least one selected from ethylene glycol, trimethylene glycol, and tetramethylene glycol, and more preferably ethylene glycol. It is preferable to use a solution in which the aluminum compound is dissolved in water or ethylene glycol, as this can significantly exhibit the effects of the present invention.

[0043] The aluminum content in the polyester resin (A) must be 9 to 19 ppm by mass, preferably 10 to 19 ppm by mass, more preferably 10 to 17 ppm by mass, and even more preferably 12 to 17 ppm by mass. If the aluminum content is less than 9 ppm by mass, the polymerization activity may not be fully exerted. On the other hand, if it exceeds 19 ppm by mass, the amount of aluminum-based foreign matter may increase.

[0044] <Phosphorus compounds> The phosphorus compound constituting the polymerization catalyst is not particularly limited, but a phosphonic acid compound or a phosphinic acid compound is preferably used because it has a large effect of improving the catalytic activity, and among these, a phosphonic acid compound is more preferably used because it has a particularly large effect of improving the catalytic activity.

[0045] Among the above phosphorus compounds, phosphorus compounds having a phosphorus element and a phenol structure in the same molecule are preferred. There are no particular limitations on the phosphorus compound as long as it has a phosphorus element and a phenol structure in the same molecule, but using one or more compounds selected from the group consisting of phosphonic acid compounds having a phosphorus element and a phenol structure in the same molecule and phosphinic acid compounds having a phosphorus element and a phenol structure in the same molecule is preferred because it has a significant effect of improving catalytic activity, and using one or more phosphonic acid compounds having a phosphorus element and a phenol structure in the same molecule is more preferred because it has a significantly significant effect of improving catalytic activity.

[0046] In addition, phosphorus compounds that have phosphorus element and phenol structure in the same molecule include P(=O)R 1 (OR 2 )(OR 3 ) and P(=O)R 1 R 4 (OR 2 ) and compounds represented by R 1 R represents a hydrocarbon group having 1 to 50 carbon atoms containing a phenol moiety, a hydrocarbon group having 1 to 50 carbon atoms and a phenol structure and a substituent such as a hydroxyl group, a halogen group, an alkoxyl group, or an amino group. 4 represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, or a hydrocarbon group having 1 to 50 carbon atoms containing a substituent such as a hydroxyl group, a halogen group, an alkoxyl group, or an amino group. 2 , R 3 R each independently represents hydrogen, a hydrocarbon group having 1 to 50 carbon atoms, or a hydrocarbon group having 1 to 50 carbon atoms containing a substituent such as a hydroxyl group or an alkoxyl group. However, the hydrocarbon group may contain a branched structure, an alicyclic structure such as cyclohexyl, or an aromatic ring structure such as phenyl or naphthyl. 2 and R 4 The ends of may be bonded together.

[0047] Examples of phosphorus compounds having a phosphorus element and a phenol structure in the same molecule include p-hydroxyphenylphosphonic acid, dimethyl p-hydroxyphenylphosphonate, diethyl p-hydroxyphenylphosphonate, diphenyl p-hydroxyphenylphosphonate, bis(p-hydroxyphenyl)phosphinic acid, methyl bis(p-hydroxyphenyl)phosphinate, phenyl bis(p-hydroxyphenyl)phosphinate, p-hydroxyphenylphosphinic acid, methyl p-hydroxyphenylphosphinate, phenyl p-hydroxyphenylphosphinate, and dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate represented by the following (Chemical Formula 1). As the phosphorus compound having a phosphorus element and a phenol structure in the same molecule, a phosphorus compound having a hindered phenol structure is particularly preferred, and dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate represented by the following (Chemical Formula 1) is particularly preferred.

[0048] [ka]

[0049] (In (Chemical Formula 1), X 1 , X 2 respectively represent hydrogen and an alkyl group having 1 to 4 carbon atoms.

[0050] Above X 1 , X 2 The number of carbon atoms in the alkyl group is preferably 1 to 4, more preferably 1 to 2. In particular, an ethyl ester having 2 carbon atoms is preferred because Irganox 1222 (manufactured by BASF) is commercially available and easily available.

[0051] The phosphorus compound in the present invention is preferably dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate shown in the above (Chemical Formula 1), but may also include modified forms of dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate. Details of the modified forms will be described later.

[0052] The phosphorus content in the polyester resin (A) is 13 to 31 ppm by mass, preferably 15 to 29 ppm by mass. If the phosphorus content is less than 13 ppm by mass, the polymerization activity may decrease and the amount of aluminum-based foreign matter may increase. On the other hand, if the phosphorus content exceeds 31 ppm by mass, the polymerization activity may decrease and the amount of phosphorus compound added increases, which is not preferable, resulting in an increase in catalyst costs.

[0053] <Mole Ratio of Phosphorus to Aluminum in Polyester Resin (A)> In the polyester resin (A), it is also important to control the molar ratio of phosphorus to aluminum (hereinafter referred to as the "residual molar ratio of phosphorus to aluminum" to distinguish it from the "additional molar ratio of phosphorus to aluminum" described below). This ratio must be 1.32 to 1.80, preferably 1.38 to 1.68. As described above, the aluminum and phosphorus in the polyester resin (A) are derived from the aluminum compound and phosphorus compound used as polymerization catalysts for the polyester resin (A), respectively. By using these aluminum and phosphorus compounds in combination in a specific ratio, a catalytically active complex is functionally formed in the polymerization system, enabling sufficient polymerization activity to be exerted. If the residual molar ratio of phosphorus to aluminum is less than 1.32, there is a risk of reduced thermal stability and thermal oxidative stability, and an increased amount of aluminum-based foreign matter. On the other hand, if the residual molar ratio of phosphorus to aluminum exceeds 1.80, the amount of phosphorus compound added becomes too large, resulting in increased catalyst costs.

[0054] In the present invention, in addition to the aluminum compound and phosphorus compound described above, other polycondensation catalysts such as antimony compounds, germanium compounds, and titanium compounds may be used in combination within the range that does not cause problems in the properties, processability, color tone, etc. of the polyester resin composition obtained by the production method of the present invention. The content of antimony element in the polyester resin composition is preferably 30 ppm by mass or less, the content of germanium element in the polyester resin composition is preferably 10 ppm by mass or less, and the content of titanium element in the polyester resin composition is preferably 3 ppm by mass or less. However, from the viewpoint of the object of the present invention, it is preferable to avoid using the above-mentioned other polycondensation catalysts as much as possible.

[0055] The intrinsic viscosity (IV) of the polyester resin (A) is preferably 0.56 dL / g or more, more preferably 0.56 to 0.65 dL / g, and even more preferably 0.58 to 0.64 dL / g. If the intrinsic viscosity of the polyester resin (A) is less than the above range, the mechanical strength and impact resistance of the molded product may be insufficient. On the other hand, if the intrinsic viscosity of the polyester resin (A) exceeds the above range, it is not preferable because the economic efficiency decreases.

[0056] [Method for producing polyester resin (A)] The method for producing the polyester resin (A) can be carried out by a method including known steps, except that a polyester polymerization catalyst consisting of an aluminum compound and a phosphorus compound is used as the catalyst, and the polymerization catalyst is added so as to satisfy the following (5) to (7). (5) The amount of aluminum element added to the resulting polyester resin (A) is 9 to 19 ppm by mass. (6) The amount of phosphorus added to the resulting polyester resin (A) is 18 to 38 mass ppm. (7) The molar ratio of the amount of phosphorus added in (6) to the amount of aluminum added in (5) (hereinafter referred to as "molar ratio of phosphorus added to aluminum") is 1.50 or more and 2.30 or less.

[0057] The method for producing the polyester resin (A) preferably comprises a first step of synthesizing a polyester or an oligomer thereof, which is a polycondensate (low-order condensate) as an intermediate, and a second step of further polycondensing the intermediate.

[0058] Furthermore, it is preferable to add a solution A1 in which an aluminum compound is dissolved and a solution B1 in which a phosphorus compound is dissolved to the intermediate after the first step and before the second step so as to satisfy the above conditions (5) to (7). The polycarboxylic acids and their ester-forming derivatives, hydroxycarboxylic acids and their ester-forming derivatives, and cyclic esters, which may be added in small amounts, used in the production of polyester resin (A) are not distilled out of the reaction system during polymerization, and almost 100% of the amount initially added to the system as a catalyst remains in the polyester resin (A) produced by polymerization. Therefore, the mass of the "polyester resin (A) to be produced" can be calculated from the amounts of these ingredients charged.

[0059] The method for producing the polyester or its oligomer, which is the low-order condensate (low polymer) used in the present invention, is not particularly limited.

[0060] The polyester resin (A) can be produced by a method incorporating conventionally known steps, except that a polyester polymerization catalyst composed of an aluminum compound and a phosphorus compound is used as the catalyst, and the aluminum content, phosphorus content, and molar ratio of phosphorus to aluminum in the polyester resin (A) are adjusted to fall within specific ranges. For example, polyethylene terephthalate can be produced by a direct esterification method in which terephthalic acid is directly reacted with ethylene glycol, and optionally other copolymerization components, followed by esterification after distillation and subsequent polycondensation under atmospheric or reduced pressure. Alternatively, dimethyl terephthalate is reacted with ethylene glycol, and optionally other copolymerization components, followed by esterification after distillation and subsequent polycondensation under atmospheric or reduced pressure. If necessary, solid-state polymerization may be performed to increase the intrinsic viscosity. Polymerization may be performed by either a batch polymerization method or a continuous polymerization method. The mass of the resulting polyester resin (A) can be calculated from the mass of the polycarboxylic acid, including dicarboxylic acids, used as raw materials.

[0061] In any of these methods, the esterification reaction or transesterification reaction may be carried out in one stage or in multiple stages. In the melt polymerization reaction, the number and size of reactors and the production conditions for each step can be selected as appropriate without any limitations. The reaction may be carried out in one stage or in multiple stages, preferably in two to five stages, more preferably three to four stages, and even more preferably three stages. The melt polymerization reaction is preferably carried out in a continuous reactor. A continuous reactor is a method in which a reactor for the esterification reaction or transesterification reaction and a melt polymerization reactor are connected by piping, and raw materials are continuously introduced into each reactor without emptying, transferred to the melt polymerization reactor via the piping, and the resin is withdrawn from the melt polymerization reactor. In this case, continuous does not necessarily mean that raw materials are introduced and withdrawn at all times; it may be intermittent, in which raw materials are introduced and withdrawn in small amounts, for example, about 1 / 10 of the reactor volume. When the polyester resin (A) is produced by a multi-stage esterification reaction or transesterification reaction and a continuous polymerization method, it is preferable to add the solution A1 in which the aluminum compound is dissolved and the solution B1 in which the phosphorus compound is dissolved to a transfer line between the final reaction tank of the multi-stage reaction (final esterification reaction tank or final esterification reaction tank) and the first polymerization reaction tank.

[0062] Alternatively, the polyester resin (A) produced by the melt polymerization method may be additionally polymerized by the solid-state polymerization method. The solid-state polymerization reaction can be carried out in a continuous apparatus, similar to the melt polycondensation reaction.

[0063] In the case of a continuous polycondensation apparatus consisting of three or more reactors (a three-stage polymerization method consisting of an initial stage, a middle stage, and a late stage), the first stage is the initial stage, the final stage is the late stage, and the stages from the second stage to the stage just before the final stage are the intermediate stages, and the reaction conditions for the polymerization reaction in the intermediate stage are preferably conditions between the reaction conditions in the initial stage and the reaction conditions in the final stage. It is preferable that the degree of increase in intrinsic viscosity achieved in each of these polymerization reaction steps is smoothly distributed.

[0064] In the present invention, the acid terminal group concentration of the intermediate (low-order condensate) produced in the first step is preferably 400 to 1500 eq / ton, more preferably 500 to 1200 eq / ton. By setting the acid terminal group concentration of the oligomer within the above range, the activity of the polymerization catalyst can be fully utilized.

[0065] In the present invention, the ratio of terminal hydroxyl groups (OH%) to the total terminal group concentration of the intermediate is preferably 45 to 70 mol%, more preferably 55 to 65 mol%. If the ratio of terminal hydroxyl groups in the oligomer is less than 45 mol%, the polycondensation activity may become unstable and the amount of aluminum-based foreign matter may increase. On the other hand, if the ratio of terminal hydroxyl groups in the oligomer exceeds 70 mol%, the polycondensation activity may decrease.

[0066] When an aluminum compound and a phosphorus compound are used as catalysts, they are preferably added in the form of a slurry or a solution, more preferably in a solvent such as water or glycol, even more preferably in water and / or glycol, and most preferably in ethylene glycol.

[0067] In the present invention, after the esterification reaction or the transesterification reaction is completed, it is preferable to add the solution A1 in which the aluminum compound is dissolved and the solution B1 in which the phosphorus compound is dissolved so that the contents (residual amounts) of the aluminum element and the phosphorus element in the polyester resin (A) fall within the ranges that satisfy the above (1) to (3).

[0068] By adding solution A1 containing an aluminum compound and solution B1 containing a phosphorus compound so that the contents (residual amounts) of aluminum and phosphorus in polyester resin (A) satisfy the above (1) to (3), a catalytically active complex is functionally formed in the polymerization system, thereby achieving sufficient polymerization activity and suppressing the generation of aluminum-based foreign matter.

[0069] Furthermore, even if the polyester resin (A) is polymerized under reduced pressure, almost 100% of the aluminum atoms in the aluminum compound that functions as a catalyst initially added to the system remain in the polyester resin (A) produced by polymerization. That is, since the amount of aluminum compound remains almost unchanged before and after polycondensation, if the amount of aluminum element added to the intermediate is 9 to 19 ppm by mass, the content of aluminum element in the polyester resin (A) will also be 9 to 19 ppm by mass.

[0070] Furthermore, when the phosphorus compound, which functions as a catalyst together with the aluminum compound, is placed in a reduced pressure environment during polymerization of the polyester resin (A), a portion (about 10 to 40%) of the amount initially added to the system as a catalyst is removed from the system, but this removal rate varies depending on the molar ratio of phosphorus to aluminum, the basicity or acidity of the aluminum-containing glycol solution or phosphorus-containing glycol solution added, the method of adding the aluminum-containing solution or phosphorus-containing solution (whether they are added as a single solution or separately), etc. Therefore, it is preferable to appropriately set the amount of phosphorus compound added so that the phosphorus content in the polyester resin (A) that becomes the final product satisfies the above (2).

[0071] In the present invention, it is preferable to simultaneously add the solution A1 containing the aluminum compound and the solution B1 containing the phosphorus compound, and a more preferred embodiment is to previously mix the solution A1 containing the aluminum compound and the solution B1 containing the phosphorus compound in the ratio to be added to the intermediate to prepare a mixed solution, and then add the one-component mixed solution to the intermediate. By implementing this embodiment, the effects of the present invention can be more stably achieved. Examples of methods for previously preparing the one-component solution include mixing the respective solutions in a tank and merging the solutions in pipes for adding the catalyst midway and mixing them. When adding the catalyst solution to a reaction vessel, it is preferable to vigorously stir the reaction vessel. When adding the catalyst solution to a pipe between reaction vessels, it is preferable to install an in-line mixer or the like so that the added catalyst solution is quickly and uniformly mixed. If solution A1 in which an aluminum compound is dissolved and solution B1 in which a phosphorus compound is dissolved are added separately, a large amount of foreign matter due to the aluminum compound is likely to be generated, which may result in a lower temperature-rising crystallization temperature or a higher temperature-falling crystallization temperature, making it impossible to obtain sufficient catalytic activity. By adding the aluminum compound and the phosphorus compound simultaneously, a complex of the aluminum compound and the phosphorus compound that brings about polymerization activity can be formed quickly and efficiently, but if they are added separately, the formation of the complex of the aluminum compound and the phosphorus compound is insufficient, and the aluminum compound that did not form a complex with the phosphorus compound may precipitate as foreign matter. Furthermore, it is preferable to add solution A1 having an aluminum compound dissolved therein and solution B1 having a phosphorus compound dissolved therein after the esterification reaction or transesterification reaction is completed, and it is more preferable to add solution A1 having an aluminum compound dissolved therein and solution B1 having a phosphorus compound dissolved therein to the intermediate after the first step and before the second step. If they are added before the esterification reaction or transesterification reaction is completed, the amount of aluminum-based foreign matter may increase.

[0072] When the polyester resin (A) is composed of at least one selected from polycarboxylic acids and their ester-forming derivatives and at least one selected from polyhydric alcohols and their ester-forming derivatives, the solution A1 having an aluminum compound dissolved therein is preferably a glycol solution having an aluminum compound dissolved therein (hereinafter referred to as aluminum-containing glycol solution A1), and the solution B1 having a phosphorus compound dissolved therein is preferably a glycol solution having a phosphorus compound dissolved therein (hereinafter referred to as phosphorus-containing glycol solution B1).

[0073] The maximum absorption wavelengths of aluminum-containing glycol solution A1 and phosphorus-containing glycol solution B1 are described below. By controlling the maximum absorption wavelengths of aluminum-containing glycol solution A1 and phosphorus-containing glycol solution B1 within a specific range, polymerization activity can be stabilized and polyester resins of stable quality can be obtained. By controlling the maximum absorption wavelengths of aluminum-containing glycol solution A1 and phosphorus-containing glycol solution B1 within a specific range, the Lewis acid / base properties of aluminum-containing glycol solution A1 and phosphorus-containing glycol solution B1 can be controlled within a specific range. It is presumed that these Lewis acid / base properties affect the complex formation reaction between aluminum compounds and phosphorus compounds, and that this complex formation reaction affects polymerization activity.

[0074] <Maximum absorption wavelength of aluminum-containing glycol solution A1> The maximum absorption wavelength of the aluminum-containing glycol solution A1 is preferably 562.0 to 572.0 nm, more preferably 567.0 to 572.0 nm. The maximum absorption wavelength of the aluminum-containing glycol solution A1 is a value obtained by adding Mordant Blue 13, an acid dye, to the aluminum-containing glycol solution A1 and then measuring the absorption spectrum of the sample solution using an ultraviolet-visible spectrophotometer; the measurement method will be described in detail later.

[0075] In order for the aluminum compound to functionally form a complex having catalytic activity with the phosphorus compound and thereby exhibit polymerization activity, it is preferable that the basicity of the aluminum compound contained in the aluminum-containing glycol solution A1 be within a specific range.

[0076] The maximum absorption wavelength of the aluminum-containing glycol solution A1 is affected by the type and amount of aluminum compound used, the type of glycol, and the temperature, pressure, time, etc., during preparation of the glycol solution. For example, it is a preferred embodiment to use an aluminum compound with an aluminum content within a specific range, or to treat the aqueous solution under reduced pressure or in vacuum when converting the aqueous solution into a glycol solution in preparing the aluminum-containing glycol solution A1.

[0077] If the absorption maximum wavelength of the aluminum-containing glycol solution A1 is below the above range, the basicity of the aluminum compound in the solution will be low, and a complex with the phosphorus compound will not be sufficiently formed, which may result in a decrease in polymerization activity or an increase in the amount of aluminum-based foreign matter.On the other hand, it is technically difficult to achieve an absorption maximum wavelength above the above range.

[0078] <Maximum absorption wavelength of phosphorus-containing glycol solution B1> The maximum absorption wavelength of the phosphorus-containing glycol solution B1 is preferably 458.0 to 465.0 nm, more preferably 460.0 to 463.0 nm, and even more preferably 461.0 to 462.0 nm. The maximum absorption wavelength of the phosphorus-containing glycol solution B1 is a value obtained by adding a Bismarck Brown aqueous solution, which is a basic dye, to the phosphorus-containing glycol solution B1 and then measuring the absorption spectrum of the sample solution using an ultraviolet-visible spectrophotometer. The measurement method will be described in detail later.

[0079] In order for the phosphorus compound to functionally form a complex having catalytic activity with the aluminum compound and thereby exhibit polymerization activity, it is preferable that the acidity of the phosphorus compound contained in the phosphorus-containing glycol solution B1 be within a specific range.

[0080] The maximum absorption wavelength of the phosphorus-containing glycol solution B1 is affected by the type and amount of phosphorus compound used, the type of glycol, and the temperature, pressure, and time during preparation of the glycol solution. If the maximum absorption wavelength of the phosphorus-containing glycol solution B1 exceeds the above range, the acidity of the phosphorus compound is low and a complex with the aluminum compound is not sufficiently formed, which is undesirable because the phosphorus compound is distilled out of the polymerization system, resulting in an increase in aluminum-based foreign matter. Conversely, if the maximum absorption wavelength is below the above range, the acidity of the phosphorus compound is high and the bond with the aluminum compound is strong, which may significantly reduce polymerization activity.

[0081] <Heat treatment of phosphorus compounds> The phosphorus compound used in the present invention is preferably heat-treated in a solvent. The solvent to be used is not limited as long as it is at least one selected from the group consisting of water and alkylene glycols. As the alkylene glycol, it is preferable to use a solvent that dissolves the phosphorus compound, and it is more preferable to use a glycol that is a constituent component of the target polyester resin (A), such as ethylene glycol. The heat treatment in the solvent is preferably carried out after dissolving the phosphorus compound, but it is not necessary for the phosphorus compound to be completely dissolved.

[0082] The heat treatment conditions are such that the heat treatment temperature is preferably 170 to 196° C., more preferably 175 to 185° C., and even more preferably 175 to 180° C. The heat treatment time is preferably 125 to 240 minutes, and more preferably 140 to 210 minutes.

[0083] The concentration of the phosphorus compound during the heat treatment is preferably 3 to 10% by mass.

[0084] The heat treatment described above makes it possible to keep the acidity of the phosphorus compound contained in the glycol solution constant, and by using the phosphorus compound in combination with an aluminum compound, it is possible to improve the polymerization activity and reduce the amount of aluminum-based foreign matter produced by the polymerization catalyst.

[0085] When the phosphorus compound used is dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, which is the phosphorus compound represented by the above (Chemical Formula 1), the heat treatment causes a partial structural change in the phosphorus compound represented by the above (Chemical Formula 1). For example, the change occurs due to elimination of t-butyl groups, hydrolysis of ethyl ester groups, and a hydroxyethyl ester exchange structure (ester exchange structure with ethylene glycol). Therefore, in the present invention, the phosphorus compound also includes structurally changed phosphorus compounds in addition to dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate represented by the above (Chemical Formula 1). Note that elimination of t-butyl groups occurs significantly at high temperatures during the polymerization process. The following shows nine phosphorus compounds in which the structure of 3,5-di-tert-butyl-4-hydroxybenzyl diethyl phosphonate has been partially modified. The amount of each structurally modified phosphorus compound in glycol solution can be quantified by P-NMR spectroscopy of the solution.

[0086] [ka]

[0087] Therefore, the phosphorus compound in the present invention includes not only dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate but also the nine modified products of dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate represented by the above chemical formula.

[0088] <Maximum absorption wavelength of the mixed solution obtained by mixing aluminum-containing glycol solution A1 and phosphorus-containing glycol solution B1> The maximum absorption wavelength of the mixed solution obtained by mixing aluminum-containing glycol solution A1 and phosphorus-containing glycol solution B1 (hereinafter simply referred to as "mixed solution") is preferably 559.0 to 560.9 nm, more preferably 559.5 to 560.8 nm, and even more preferably 559.7 to 560.6 nm. The maximum absorption wavelength of the mixed solution is a value obtained by adding Mordant Blue 13, an acid dye, to the mixed solution and then measuring the absorption spectrum of the sample solution using a UV-visible spectrophotometer; the measurement method will be described in detail below.

[0089] By setting the absorption maximum wavelength of the mixed solution within the above range, the complex formation reaction between the aluminum compound and the phosphorus compound can be maintained in a favorable state for both improving polymerization activity and suppressing aluminum-based contaminants, which is preferable. On the other hand, if the absorption maximum wavelength exceeds the above range, the basicity of the mixed solution is high, and the polymerization system of the polyester resin is acidic. Therefore, when the mixed solution is added to the polymerization system, the aluminum compound may neutralize with the carboxyl group terminal of the polyester resin to form a contaminant, and the amount of aluminum-based contaminants may increase. Conversely, if the absorption maximum wavelength is below the above range, the basicity of the mixed solution may be too low, causing the coordination between the aluminum compound and the phosphorus compound to become strong, which may reduce polymerization activity.

[0090] The polyester resin (A) preferably has an aluminum element content corresponding to aluminum-based foreign matter in the polyester resin (A) of 3000 ppm by mass or less, more preferably 2800 ppm by mass or less. Aluminum-based foreign matter originates from the aluminum compound used as a polymerization catalyst and is insoluble in the polyester resin (A). If the aluminum-based foreign matter content exceeds the above range, fine foreign matter insoluble in the polyester resin (A) may cause deterioration in the quality of the film. This also leads to issues such as increased filter clogging during polyester filtration in the polycondensation process and film-forming process. The preferred lower limit of the aluminum element content corresponding to aluminum-based foreign matter is 0 ppm by mass, but due to technical difficulties, it is approximately 300 ppm by mass. As can be seen from the fact that the amount of aluminum element is measured using the measurement method described later in the Examples, this index is used to relatively evaluate the amount of aluminum-based foreign matter, and does not indicate the absolute value of the amount of aluminum-based foreign matter contained in the polyester resin (A).

[0091] [Masterbatch containing antiblocking agent (B)] By using a masterbatch (B) containing an antiblocking agent, when the polyester resin composition produced by the present invention is formed into a film, the antiblocking agent forms surface protrusions on the surface of the resulting polyester film, thereby improving the handling properties of the film, such as slipperiness, running properties, abrasion resistance, and winding properties.

[0092] The type of polyester resin constituting the masterbatch (B) is not limited, but it is preferably the same polyester resin as the base polyester resin (A).

[0093] The volume average particle diameter of the antiblocking agent contained in the masterbatch (B) is preferably 0.5 to 3.0 μm, more preferably 0.8 to 2.5 μm, and even more preferably 2.0 to 2.5 μm. If the volume average particle diameter of the antiblocking agent is less than 0.5 μm, the effect of imparting handleability, such as slipperiness and runnability, to the film may be reduced. On the other hand, if the volume average particle diameter of the antiblocking agent exceeds 3.0 μm, the quality of the film may be impaired due to the formation of coarse protrusions. The volume average particle diameter of the antiblocking agent can be determined from the particle size distribution measured by laser light scattering using water or ethylene glycol as a medium; detailed measurement methods are described below.

[0094] The content of the antiblocking agent in the masterbatch (B) is preferably in the range of 0.5 to 20% by mass, more preferably in the range of 0.6 to 15% by mass. If it is less than 0.5% by mass, the amount of masterbatch (B) needs to be increased, which is economically disadvantageous. Conversely, if it exceeds 20% by mass, aggregation of the antiblocking agent occurs, increasing the number of coarse particles, which may cause problems such as clogging of filters used to clarify the polymer in the film-forming process or an increase in surface defects when the film is formed.

[0095] <Insoluble particles> The masterbatch (B) preferably contains insoluble particles that are insoluble in the polyester resin (A). That is, the antiblocking agent preferably contains insoluble particles that are insoluble in the polyester resin (A). The volume average particle diameter of the insoluble particles is more preferably 0.5 to 3.0 μm, and the content of the insoluble particles is more preferably 0.5 to 20 mass%. The insoluble particles used in the present invention are not particularly limited as long as they are insoluble in the polyester resin (A), and may be inorganic particles or organic particles. Alternatively, they may be inorganic-organic composite particles.

[0096] The type of the inorganic particles is not particularly limited, and examples thereof include oxides, carbonates, silicates, sulfates, and aluminates of metals such as titanium, aluminum, silicon, calcium, magnesium, and barium.

[0097] Specific examples of the inorganic particles include titanium dioxide, alumina, aluminosilicate, silicon dioxide, calcium oxide, calcium carbonate, barium sulfate, and naturally occurring talc, mica, kaolinite, and zeolite, but are not limited to these.

[0098] The type of the organic particles is not particularly limited, and examples thereof include silicone-based, crosslinked polyacrylic acid-based, and benzoguanamine resin-based particles.

[0099] The insoluble particles are preferably silica particles, since a highly transparent polyester film can be obtained.

[0100] [Manufacturing method of masterbatch (B)] The method for producing the masterbatch (B) is not particularly limited, and may be, for example, a polymerization step addition method in which a slurry of the antiblocking agent is added in the polymerization step of the polyester resin, or a so-called melt kneading method in which the antiblocking agent is mixed with the polyester resin in a molten state.

[0101] <Polymerization process addition method> The timing of addition of the antiblocking agent slurry in the polymerization step addition method is not limited. It may be added at any time from the beginning of the transesterification reaction step or esterification reaction step to the start of initial polymerization. It may be added directly to the reaction vessel, or may be added to the transfer line between the reaction vessels using a mixer or the like. It may also be added by installing an addition vessel. In order to prevent aggregation of the antiblocking agent, it is more preferable to add the antiblocking agent after forming a slurry with glycols and then mechanically dispersing the slurry with a medium-agitation disperser such as a sand grinder, attritor, or ultrasonic wave, and then adding an alkali metal compound, an ammonium compound, or a phosphorus compound to improve dispersion efficiency.

[0102] The amount of antiblocking agent added in the polymerization step is preferably 0.5 to 2.0% by mass, more preferably 0.6 to 1.8% by mass. If the amount is less than 0.5% by mass, the antiblocking agent may aggregate after blending and diluting, resulting in increased generation of coarse particles. If the amount is more than 2.0% by mass, the effect of preventing coarse particles may be insufficient, and foreign matter may be generated when the film is formed.

[0103] <Melt kneading method> The melt-kneading method is not limited, and may be carried out using a single-screw or multi-screw kneader, or may be carried out using a kneader.

[0104] The amount of antiblocking agent added in the melt-kneading method is preferably 2.0 to 20% by mass, and more preferably 3.0 to 15% by mass, relative to the polyester resin used in the masterbatch (B). If the amount of antiblocking agent added is less than 2.0% by mass or more than 20% by mass, the dispersibility of the antiblocking agent in the polyester resin may be poor, and the amount of coarse particles, which are aggregates of the antiblocking agent, may increase.

[0105] The melt-kneading method may be carried out by melting the polyester resin, or by attaching a kneading device to the outlet of the polyester resin polymerization process.

[0106] The polymerization catalyst for the polyester resin used in the masterbatch (B) is not limited, but is preferably the same as the catalyst used in the production of the polyester resin (A). That is, the polyester resin used in the masterbatch (B) is preferably produced using a polymerization catalyst consisting of an aluminum compound and a phosphorus compound.

[0107] [Masterbatch containing electrostatic adhesion agent (C)] When a polyester resin composition containing a masterbatch (C) containing an electrostatic adhesion imparting agent (hereinafter sometimes referred to as "masterbatch (C)") is formed into a film, the electrostatic adhesion of the sheet-like material to the cooling drum can be improved in the electrostatic adhesion casting method, thereby achieving effects such as improved film productivity and reduced thickness unevenness in the film, thereby improving the productivity and quality of the polyester film.

[0108] The type of polyester resin constituting the masterbatch (C) is not limited, but it is preferably the same polyester resin as the polyester resin (A).

[0109] The melt resistivity of the masterbatch (C) is 0.005 x 10 8 ~0.05×10 8 Ω·cm is preferred, and 0.005×10 8 ~0.025×10 8 It is more preferable that the melt resistivity of the masterbatch is 0.05×10 8 If the melt resistivity of the masterbatch (C) is higher than Ω·cm, it is necessary to add a large amount of the masterbatch (C) to improve the film-forming properties of the polyester resin composition, which causes problems such as an increase in production costs. 8 It is technically difficult to achieve a resistance of less than Ω·cm. In order to improve the film-forming properties of the polyester film, the melt resistivity of the polyester film formed from the polyester resin composition containing the masterbatch (C) is 0.1 × 10 8 ~0.3×108 Ω·cm is preferred, and 0.15×10 8 ~0.25×10 8 It is more preferable that the melt resistivity is Ω·cm. The melt resistivity can be measured by the method described in the Examples section below.

[0110] To the masterbatch (C), a magnesium compound or an alkali metal compound is preferably added to reduce the melt resistivity. Furthermore, to disperse these metal ion components in the polyester resin composition without converting them into foreign matter and to further improve thermal stability, a phosphorus compound is preferably added. The masterbatch (C) preferably contains 400 to 2700 ppm by mass of magnesium, 40 to 270 ppm by mass of alkali metal, and 200 to 1700 ppm by mass of phosphorus.

[0111] The magnesium compound used in the present invention can be any known magnesium compound. For example, lower fatty acid salts such as magnesium acetate and alkoxides such as magnesium methoxide can be used. These can be used alone or in combination of two or more. Magnesium acetate is particularly preferred.

[0112] The masterbatch (C) preferably contains 400 to 2700 ppm by mass of magnesium element. If the amount of magnesium element is less than 400 ppm by mass, the melt resistivity will be high, and a large amount of masterbatch (C) will need to be added to improve the film-forming properties of the polyester resin composition, which may result in problems such as low efficacy as a masterbatch and increased production costs. If the amount of magnesium element exceeds 2700 ppm by mass, the amount of insoluble foreign matter (magnesium salts) produced will increase, and heat resistance may decrease, resulting in severe coloration of the film. The amount of magnesium element is more preferably 450 to 2500 ppm by mass, and even more preferably 450 to 2000 ppm by mass.

[0113] Examples of the alkali metal of the alkali metal compound contained in the masterbatch (C) include lithium, sodium, and potassium. Examples of the alkali metal compound include lower fatty acid salts having 2 to 4 carbon atoms, such as lithium acetate and potassium acetate, and alkoxides such as potassium methoxide. These may be used alone or in combination of two or more. Potassium is preferred as the alkali metal, as it has a significant effect of lowering the melt resistivity. The alkali metal compound is preferably a lower fatty acid salt having 2 to 4 carbon atoms, more preferably an alkali metal acetate, and even more preferably potassium acetate.

[0114] The masterbatch (C) preferably contains 40 to 270 ppm by mass of alkali metal element. If the amount of alkali metal element is less than 40 ppm by mass, the melt resistivity increases, and a large amount of masterbatch (C) needs to be added to improve the film formability of the polyester resin composition, which may result in problems such as reduced efficacy as masterbatch (C) and increased production costs. If the amount of alkali metal element exceeds 270 ppm by mass, the effect of improving the melt resistivity may saturate, and the heat resistance may decrease, resulting in severe coloration of the film. The amount of alkali metal element is more preferably 45 to 250 ppm by mass, and even more preferably 45 to 200 ppm by mass.

[0115] Examples of phosphorus compounds contained in the masterbatch (C) include phosphoric acid, phosphorous acid, hypophosphorous acid, phosphonic acid, phosphinic acid, and ester compounds thereof. Examples include phosphoric acid, trimethyl phosphate, tributyl phosphate, triphenyl phosphate, monomethyl phosphate, dimethyl phosphate, monobutyl phosphate, dibutyl phosphate, phosphorous acid, trimethyl phosphite, tributyl phosphite, methylphosphonic acid, dimethyl methylphosphonate, dimethyl ethylphosphonate, dimethyl phenylphosphonate, diethyl phenylphosphonate, diphenyl phenylphosphonate, ethyl diethyl phosphonoacetate, phosphinic acid, methylphosphinic acid, dimethylphosphinic acid, phenylphosphinic acid, diphenylphosphinic acid, methyl dimethylphosphinate, and methyl diphenylphosphinate. To significantly exhibit the effects of the present invention, at least one selected from the group consisting of trialkyl phosphates and ethyl diethyl phosphonoacetates is preferred, and trialkyl phosphates are more preferred. Among the trialkyl phosphate esters, it is more preferable that at least one of the alkyl groups of the alkyl ester is an alkyl group having 2 to 4 carbon atoms, and it is particularly preferable that all of the alkyl groups of the alkyl ester are alkyl groups having 2 to 4 carbon atoms. Specific examples of particularly preferable phosphorus compounds include triethyl phosphate, tripropyl phosphate, and tributyl phosphate, and these may be used alone or in combination of two or more. In particular, triethyl phosphate is most preferable because it is thought to form a complex with an appropriately strong interaction with magnesium ions, and a masterbatch (C) can be obtained that has low melt resistivity, little foreign matter, and excellent color tone.

[0116] The masterbatch (C) preferably contains 200 to 1700 ppm by mass of phosphorus. If the amount of phosphorus is less than 200 ppm by mass, the effect of stabilizing magnesium ions and alkali metal ions and dispersing them in the polyester resin composition will be reduced, which may result in a large amount of insoluble magnesium-based foreign matter being generated. Furthermore, the magnesium that has become foreign matter will no longer have the effect of reducing the melt resistivity, which may result in an increase in the melt resistivity. This may also lead to a decrease in heat resistance and severe discoloration of the film. If the amount of phosphorus exceeds 1700 ppm by mass, the excess phosphorus compound will interact with the magnesium ions, and the charge of the magnesium ions will not contribute to the effect of reducing the melt resistivity, which may result in an increase in the melt resistivity despite the large amount of magnesium added. A more preferred amount of phosphorus is 220 to 1000 ppm by mass.

[0117] The contents of magnesium, alkali metal, and phosphorus in masterbatch (C) can be quantified by the method described in the Examples below. There are no particular restrictions on the timing of adding the magnesium compound, alkali metal compound, and phosphorus compound to the polyester resin used in masterbatch (C), but adding them during polyester polymerization, particularly during the esterification (or transesterification) step, or between the end of the esterification (or transesterification) step and the start of the polycondensation step, is preferred because it prevents the acid component of the polyester from forming a salt with the magnesium ion or alkali metal ion and becoming a foreign substance, and also enables uniform dispersion in the oligomer. When these compounds are added during polyester polymerization, the magnesium element and alkali metal element remain in the polyester resin composition in almost the same amounts as added, but the phosphorus element may be distilled out of the polymerization system under reduced pressure. Therefore, it is necessary to determine the amount of phosphorus compound to be added by understanding in advance the relationship between the added amount and the remaining amount.

[0118] When the polyester resin used in the masterbatch (C) is a polyester resin containing a dicarboxylic acid component and a glycol component as constituent components, the effects of the present invention can be achieved by satisfying the following formula (4) when the amount of magnesium element relative to the dicarboxylic acid component is mm mol %, the amount of alkali metal element is k mol %, and the amount of phosphorus element is p mol %: (4) 2≦(m+k / 2) / p≦3.5 It is thought that the phosphorus atoms stabilize the magnesium ions and alkali metal ions without turning them into foreign substances. Because magnesium ions are divalent and alkali metal ions are monovalent, the sum of the amounts of magnesium ions and alkali metal ions is expressed as (m+k / 2), and the ratio obtained by dividing this by p, (m+k / 2) / p, is the relative amount of magnesium ions and alkali metal ions to the phosphorus atoms. If the value of (m+k / 2) / p exceeds 3.5, the amount of phosphorus element is relatively small compared to the magnesium element and alkali metal element, which reduces the effect of stabilizing magnesium ions and alkali metal ions and dispersing them in the polyester resin composition, resulting in a large amount of insoluble foreign matter (magnesium salts, alkali metal salts) being produced. Furthermore, the foreign magnesium loses its effect of reducing the melt resistivity, resulting in a high melt resistivity relative to the amount of magnesium added. This also leads to a decrease in heat resistance and a deterioration in the color tone of the masterbatch (C) and film. If the value of (m+k / 2) / p is less than 2, the amount of phosphorus will be in excess relative to the magnesium and alkali metal elements, and the excess phosphorus compound will interact with the magnesium ions, improving the color tone deterioration. However, the charge on the magnesium ions will not contribute to the effect of lowering the melting resistivity, and the melting resistivity will increase relative to the amount of magnesium added. (m+k / 2) / p is more preferably 2.3 or more and 3 or less, and even more preferably 2.5 or more and 3 or less. In other words, the effect of reducing the melting resistivity and the color tone are trade-offs. Therefore, by satisfying formula (4), both the effect of reducing the melting resistivity and the color tone can be achieved.

[0119] The polymerization catalyst for the polyester resin used in the masterbatch (C) is not limited, but is preferably the same as the catalyst used in the production of the polyester resin (A). Since the compound used as the electrostatic adhesion imparting agent also acts as a co-catalyst, it is not necessary to use a phosphorus compound among the catalysts used in the production of the polyester resin (A), i.e., only an aluminum compound may be used.

[0120] [Anti-blocking agent / electrostatic adhesion agent composite masterbatch (D)] The antiblocking agent / electrostatic adhesion-imparting agent composite masterbatch (D) (hereinafter referred to as "composite masterbatch (D)" or "masterbatch (D)") of the present invention combines the compositions and properties of the antiblocking agent masterbatch (B) and the electrostatic adhesion-imparting agent masterbatch (C). Therefore, instead of masterbatch (B), masterbatch (D) can be mixed with the base polyester resin (A). By using a polyester resin composition containing the composite masterbatch (D) and polyester resin (A), similar to a polyester resin composition containing polyester resin (A), masterbatch (B), and masterbatch (C), electrostatic adhesion can be improved when producing a polyester film from the polyester resin composition, thereby improving the productivity of the polyester film. Furthermore, by forming surface protrusions on the surface of the resulting polyester film using the antiblocking agent, handling properties such as slipperiness, running properties, abrasion resistance, and winding properties of the film can be improved.

[0121] The composite masterbatch (D) preferably contains insoluble particles that are insoluble in the polyester resin (A), the insoluble particles having a volume average particle size of 0.5 to 3.0 μm, and a content of the insoluble particles of 0.5 to 20 mass %. The composite masterbatch (D) preferably contains 400 to 2700 mass ppm of magnesium, 40 to 270 mass ppm of alkali metal, and 200 to 1700 mass ppm of phosphorus.

[0122] The volume average particle size and content of the antiblocking agent contained in the composite masterbatch (D) are preferably in the same ranges as those of the volume average particle size and content of the antiblocking agent in the masterbatch (B), for the same reasons as those described in the section regarding the masterbatch (B).

[0123] The contents of magnesium, alkali metal, and phosphorus in the composite masterbatch (D) are preferably in the same ranges as the contents of magnesium, alkali metal, and phosphorus in the masterbatch (C), for the same reasons as those described in the section on masterbatch (C).

[0124] The contents of magnesium, alkali metal, and phosphorus in the composite masterbatch (D) can be quantified by the method described in the Examples below, similar to the contents of the above elements in masterbatch (C). The timing of adding the magnesium compound, alkali metal compound, and phosphorus compound to the polyester resin used in composite masterbatch (D) is not particularly limited, but adding them during polyester polymerization, particularly during the esterification (or transesterification) step, or between the end of the esterification (or transesterification) step and the start of the polycondensation step, is preferred because it prevents the magnesium ions and alkali metal ions from forming salts with the acid component of the polyester and becoming foreign substances, and also allows for uniform dispersion in the oligomer. When these compounds are added during polyester polymerization, the magnesium element and alkali metal element remain in the polyester resin composition in almost the same amounts as added, but the phosphorus element may be distilled out of the polymerization system under reduced pressure. Therefore, it is necessary to determine the amount of phosphorus compound to be added by understanding in advance the relationship between the added amount and the remaining amount.

[0125] When the polyester resin used in the composite masterbatch (D) is a polyester resin containing a dicarboxylic acid component and a glycol component as constituent components, the effects of the present invention can be achieved by the molar ratio of magnesium atoms, alkali metal atoms, and phosphorus atoms satisfying the above-mentioned formula (4), where m (mol%) is the amount of magnesium atoms, k (mol%) is the amount of alkali metal atoms, and p (mol%) is the amount of phosphorus atoms relative to the dicarboxylic acid component. The reasons for this are the same as those described in the section on masterbatch (C).

[0126] The polymerization catalyst for the polyester resin used in the composite masterbatch (D) is not limited, but is preferably the same as the catalyst used in the production of the polyester resin (A). Since the compound used as the electrostatic adhesion imparting agent also acts as a co-catalyst, it is not necessary to use a phosphorus compound among the catalysts used in the production of the polyester resin (A), i.e., only an aluminum compound may be used.

[0127] The method for producing the composite masterbatch (D) is not particularly limited. For example, a slurry solution of the antiblocking agent and the components constituting the masterbatch (C) described above may be added during the production process of the polyester resin used in the composite masterbatch (D), or the composite masterbatch (D) may be produced by melt-kneading the masterbatch (B) and the masterbatch (C). Furthermore, the antiblocking agent and the electrostatic adhesion imparting agent may be added during the production process of the polyester resin used in the composite masterbatch (D).

[0128] [others] The polyester resin composition used in the present invention preferably does not contain any resin other than the polyester resin, but may contain resins other than the polyester resin as long as the object of the present invention is not impaired. The resin other than the polyester resin is not particularly limited, but examples thereof include polyolefin resin, polyamide resin, and polyacetal resin. The content of resin other than the polyester resin in the polyester resin composition is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, particularly preferably 3% by mass or less, and most preferably 1% by mass or less. The method for blending the above resins with the polyester resin is not particularly limited, and examples thereof include adding the resins during the polyester resin production process, dry blending with the polyester resin after production, or other methods that allow for uniform mixing.

[0129] In the polyester resin composition used in the present invention, one or more of various additives such as diethylene glycol inhibitors, fluorescent brighteners, color adjusters such as dyes and pigments, UV inhibitors, infrared absorbing dyes, heat stabilizers, surfactants, and antioxidants can be contained in one or more of the polyester resin (A) and masterbatches (B) to (D) depending on the intended use. Examples of diethylene glycol inhibitors that can be used include basic compounds such as alkylamine compounds and ammonium salt compounds. Examples of antioxidants that can be used include aromatic amine-based and phenol-based antioxidants. Examples of stabilizers that can be used include sulfur-based and amine-based stabilizers. These additives can be added in an amount of preferably 10% by mass or less, more preferably 5% by mass or less, based on the polyester resin composition.

[0130] [Polyester film] A polyester film can be obtained by forming the polyester resin composition obtained by the production method of the present invention into a film. The polyester film may have a single layer structure or a multilayer structure having two or more layers.

[0131] The single-layer polyester film is preferably formed by forming a polyester resin composition containing a polyester resin (A) and a masterbatch (B). More preferably, the content of insoluble particles in the film is 500 to 2000 mass ppm, and the melt resistivity of the film is 0.15 to 0.6 × 10 8 The monolayer polyester film is formed by forming a film from a polyester resin composition in which polyester resin (A), masterbatch (B), and masterbatch (C) are blended so that the dielectric constant is Ω·cm, or the monolayer polyester film is formed by forming a film from a polyester resin composition in which polyester resin (A) and composite masterbatch (D) are blended. The content of insoluble particles in the single-layer polyester film is more preferably 600 to 1800 mass ppm. The melt resistivity of the single-layer polyester film is more preferably 0.15 to 0.4×10 8 It is more preferable that the resistivity is Ω·cm.

[0132] In the case of a multi-layered polyester film, the composition of each layer may be changed so as to have the above-mentioned properties, or all layers may have the same composition. For example, when a polyester film has a three-layer structure consisting of a surface layer A, an intermediate layer, and a surface layer B, it is preferable to blend an antiblocking agent into at least one (preferably both) of the polyester compositions forming the surface layer A and the surface layer B, but not into the polyester composition forming the intermediate layer. The presence of an antiblocking agent in the surface layer of the polyester film forms surface protrusions on the surface of the polyester film, thereby improving the handling properties of the film, such as slipperiness, running properties, abrasion resistance, and winding properties. Blending an antiblocking agent into both the polyester compositions forming the surface layer A and the surface layer B is more preferable, as it significantly enhances the effect of blending the antiblocking agent. On the other hand, blending an antiblocking agent into the polyester composition forming the intermediate layer is not essential. Rather, not blending an antiblocking agent into the polyester composition forming the intermediate layer is preferable, as it suppresses the decrease in film transparency caused by the antiblocking agent and significantly improves the transparency of the resulting film.

[0133] In the case of a multi-layer polyester film, it is also preferable to blend the masterbatch (C) containing an agent for imparting electrostatic adhesion or the composite masterbatch (D) in all layers in order to improve electrostatic adhesion.

[0134] In the case of a multilayer structure, the number of layers and thickness ratio are not limited, but a three-layer structure with a thickness ratio of surface layer / intermediate layer / surface layer of 0.05 / 0.9 / 0.05 to 0.2 / 0.6 / 0.2 is preferred. By providing a film with this three-layer structure, the transparency of the film can be increased while thickness unevenness of the film can be reduced.

[0135] When using recycled polyester resin recovered from film manufacturing waste such as cuts or defective parts at both ends of a film generated during the film manufacturing process, in the above-mentioned three-layer film, by blending recycled polyester resin recovered from film manufacturing waste such as cuts or defective parts at both ends of a film generated during the film manufacturing process into the middle layer, it is possible to suppress the occurrence of film surface defects caused by foreign matter mixed in the cuts or recycled polyester resin.

[0136] When forming a film having the above three-layer structure, it is preferable to form a film by melt-extruding a polyester resin composition containing polyester resin (A) and masterbatch (B) so that the content of insoluble particles in the surface layer of one side (preferably both sides) is 500 to 2000 ppm by mass. The content of insoluble particles in the surface layer is more preferably 600 to 1800 ppm by mass. Furthermore, a composite masterbatch (D) may be used instead of masterbatch (B). The use of composite masterbatch (D) can improve the transparency of the polyester film and increase economic efficiency.

[0137] Even when using a film with the above three-layer structure, the melt resistivity of the film must be 0.15 to 0.6 × 10 8 It is preferable that the melt resistivity of the film satisfies the above range. It is preferable that the masterbatch (C) is blended into the polyester resin composition forming any layer so that the melt resistivity of the film falls within the above range. However, a composite masterbatch (D) may be used instead of the masterbatch (C). The melt resistivity of the film is 0.15 to 0.4 × 10 8 It is more preferable that the resistivity is Ω·cm.

[0138] This application claims the benefit of priority to Japanese Patent Application No. 2020-153075, filed on September 11, 2020. The entire content of the specification of Japanese Patent Application No. 2020-153075, filed on September 11, 2020, is incorporated herein by reference. [Example]

[0139] The present invention will be described below with reference to examples, but the present invention is not limited to these examples. The evaluation methods used in each example and comparative example are as follows.

[0140] [Evaluation method] (1) Maximum absorption wavelength of aluminum-containing ethylene glycol solution a1 After adding 4 mL of ethylene glycol and 0.3 mL of a 1 mmol / L Mordant Blue 13 aqueous solution to a 6 mL sample bottle, 0.1 mL of aluminum-containing ethylene glycol solution a1 (described below) was added, the bottle was capped, and the solution was shaken for 10 seconds until homogeneous. After allowing the solution to stand at room temperature (23°C) for 10 minutes, the absorption spectrum of the sample solution was measured using a UV-visible spectrophotometer under the conditions below to determine the maximum absorption wavelength of aluminum-containing ethylene glycol solution a1. Note that in this measurement, room temperature is defined as 15 to 30°C, and the entire procedure was carried out in a room within this temperature range. Equipment: Shimadzu UV-1800 UV-visible spectrophotometer Spectral bandwidth: 1 nm Sample cell: Square cell (material: polymethyl methacrylate (PMMA), optical path length: 10 mm) Control solution: ethylene glycol Scan range: 400~700nm Scan speed setting: 0.05 sec Scan pitch: 0.2 nm Number of scans: 1

[0141] (2) Maximum absorption wavelength of phosphorus-containing ethylene glycol solutions b1 and b1' After adding 4 mL of ethylene glycol and 0.3 mL of 1 mmol / L Bismarck Brown aqueous solution to a 6 mL sample bottle, 0.1 mL of phosphorus-containing ethylene glycol solution b1 was added, the bottle was capped, and the solution was shaken for 10 seconds until homogeneous. After leaving the solution at room temperature (23°C) for 10 minutes, the absorption spectrum of the sample solution was measured using a UV-visible spectrophotometer under the following conditions to determine the maximum absorption wavelength of phosphorus-containing ethylene glycol solution b1. Note that in this measurement, room temperature is defined as 15 to 30°C, and the entire procedure was carried out in a room within this temperature range. Equipment: Shimadzu UV-1800 UV-visible spectrophotometer Spectral bandwidth: 1 nm Sample cell: Square cell (material: PMMA, optical path length: 10 mm) Control solution: ethylene glycol Scan range: 400~700nm Scan speed setting: 0.05 sec Scan pitch: 0.2 nm Number of scans: 1 In addition, the maximum absorption wavelength of the phosphorus-containing ethylene glycol solution b1' was determined by the same evaluation method as above, except that the phosphorus-containing ethylene glycol solution b1 was changed to the phosphorus-containing ethylene glycol solution b1'.

[0142] (3) Maximum absorption wavelength of the mixture of aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 or b1' To a 6 mL sample bottle, 4 mL of ethylene glycol and 0.3 mL of 1 mmol / L Mordant Blue 13 aqueous solution were added, followed by 0.1 mL of a mixture of aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 or b1'. The sample bottle was then capped and shaken for 10 seconds until the solution was homogenous. After allowing the solution to stand at room temperature (23°C) for 10 minutes, the absorption spectrum of the sample solution was measured using a UV-visible spectrophotometer under the following conditions to determine the maximum absorption wavelength. The mixing ratio of aluminum-containing ethylene glycol solution a1 to phosphorus-containing ethylene glycol solution b1 or b1' in the mixture was the same as the mixing ratio of aluminum-containing ethylene glycol solution a1 to phosphorus-containing ethylene glycol solution b1 or b1' in each example. In this measurement, room temperature was defined as 15 to 30°C, and the entire procedure was carried out in a room within this temperature range. Equipment: Shimadzu UV-1800 UV-visible spectrophotometer Spectral bandwidth: 1 nm Sample cell: Square cell (material: PMMA, optical path length: 10 mm) Control solution: ethylene glycol Scan range: 400~700nm Scan speed setting: 0.05 sec Scan pitch: 0.2 nm Number of scans: 1

[0143] (4) Volume average particle size of silica particles Using a laser light scattering particle size distribution analyzer (Leeds & Northrup, Microtrac HRA model: 9320-X100), the ethylene glycol slurry of silica particles was diluted with water and measured in a substantially aqueous system. The cumulative 50% volume diameter of the measurement result was taken as the volume average particle diameter.

[0144] (5) Intrinsic viscosity (IV) of polyester resin (A), masterbatch (C), and masterbatch (D) The polyester resin (A) was dissolved in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (mass ratio: 3 / 2), and the intrinsic viscosity was measured at a temperature of 30° C. The intrinsic viscosity of the master batch (C) and the master batch (D) was also measured in the same manner as the intrinsic viscosity of the polyester resin (A).

[0145] (6) Content of aluminum element in polyester resin (A) and masterbatch (C) Polyester resin (A) was weighed into a platinum crucible, carbonized on an electric stove, and then incinerated in a muffle furnace at 550°C for 8 hours. The incinerated sample was dissolved in 1.2M hydrochloric acid to prepare a sample solution. The aluminum concentration in the polyester resin (A) was determined using high-frequency inductively coupled plasma emission spectrometry. Equipment: SPECTRO CIROS-120 Plasma output: 1400W Plasma gas: 13.0 L / min Auxiliary gas: 2.0L / min Nebulizer: Crossflow nebulizer Chamber: Cyclone chamber Measurement wavelength: 167.078nm In addition, the aluminum element concentration in the masterbatch (C) was also determined by the same method as in the polyester resin (A).

[0146] (7) Phosphorus content in polyester resin (A) Polyester resin (A) was subjected to wet decomposition with sulfuric acid, nitric acid, and perchloric acid, followed by neutralization with aqueous ammonia. Ammonium molybdate and hydrazine sulfate were added to the resulting solution, and the absorbance at a wavelength of 830 nm was measured using a UV-visible spectrophotometer (Shimadzu Corporation, UV-1700). The phosphorus concentration in polyester resin (A) was determined from a previously prepared calibration curve.

[0147] (8) Amount of aluminum-based foreign matter 30 g of polyester resin (A) and 250 mL of a mixed solution of p-chlorophenol / tetrachloroethane (3 / 1: mass ratio) were placed in a 500 mL Erlenmeyer flask equipped with a stirrer and heated to 100-105°C for 1.5 hours using a hot stirrer to dissolve the mixture. The solution was filtered to remove foreign matter using a polytetrafluoroethylene membrane filter (PTFE membrane filter manufactured by Advantec, product name: T100A047A) with a diameter of 47 mm and a pore size of 1.0 μm. The effective filtration diameter was 37.5 mm. After filtration, the filter was washed with 50 mL of chloroform and then dried. The aluminum content of the filtration surface of the membrane filter was quantified using a scanning X-ray fluorescence analyzer (RIGAKU Corporation, ZSX100e, Rh line bulb 4.0 kW). Quantification was performed on the central 30 mm diameter portion of the membrane filter. The calibration curve for the X-ray fluorescence analysis was obtained using polyethylene terephthalate resin with a known aluminum content, and the apparent aluminum content was expressed in ppm. Measurements were performed at an X-ray output of 50 kV and 70 mA, using pentaerythritol as the analyzing crystal and a PC (proportional counter) as the detector, and measuring the Al-Kα line intensity at a PHA (pulse height analyzer) setting of 100-300. The aluminum content in the PET resin for the calibration curve was quantified using high-frequency inductively coupled plasma atomic emission spectrometry.

[0148] (9) Back pressure rise coefficient (k) Polyester resin (A) was vacuum dried at 140°C for 16 hours, then fed to a melt extruder, and the extruder outlet pressure was controlled to 1.96 MPa. A spinning test was carried out for 4 hours at a spinning temperature of 295°C and a discharge rate of 6 g / min using a filter with a filter diameter of 14 mm. During the spinning test, the filter pressure was recorded every 30 minutes, and the back pressure increase per unit time, ΔP (MPa / hour), was calculated using the pressure (MPa) value 4 hours after the start of spinning and the pressure (MPa) value at the start of spinning. The spinning nozzle used had 12 orifices with a hole diameter of 0.23 mm and a length of 0.3 mm. The filters used were, in order from the extruder outlet, a 100-mesh wire mesh, a 10 μm Naslon filter, a 100-mesh wire mesh, and a 50-mesh wire mesh. The back pressure rise coefficient k is the back pressure rise per unit time ΔP (MPa / hour), the flow rate Q (kg / hour), and the filtration area S (cm 2 ) was calculated using the following formula: k=ΔP / (Q / S) The area S was calculated from the filter diameter, and the flow rate Q was calculated from the discharge amount.

[0149] (10) Color tone (Co-b) Using a colorimeter (ZE-6000, manufactured by Nippon Denshoku Industries Co., Ltd.), Co-b was measured using the tristimulus values ​​XYZ, which express the basic stimulus amount of a color. The higher the Co-b value, the stronger the yellowness.

[0150] (11) Number of coarse particles in masterbatch (B) Polyester resin chips were prepared by diluting and kneading masterbatch (B) with polyester resin (A) to a concentration of 0.12% by mass of SiO2 particles. Each chip was sandwiched between two cover glasses (Matsunami microcover glasses, 25 mm x 25 mm, 0.2 mm thick), heated to approximately 300 °C on a hot plate, pressed to a thickness of 0.8–0.9 mm, and immediately quenched to prepare a specimen for observation. The central portion of the specimen was observed using a phase-contrast microscope (Nikon, OPTIPHOT) and an objective lens (Nikon, 10x magnification, 0.5 aperture). Images were captured via a CCD camera and analyzed by an image analyzer (Nireco, LUZEX AP). The number of particles with a diameter of 10 μm or larger was counted. Similar measurements were performed 20 times, changing the field of view, to determine the total particle count. The total particle count was calculated for a field of view area of ​​1 mm. 2 The number of particles with a particle size of 10 μm or more per unit area was calculated and taken as the number of coarse particles. In addition, in the composite masterbatch (D), the number of coarse particles was determined by the same method as in the masterbatch (B).

[0151] (12) Contents of magnesium, potassium, and phosphorus elements in masterbatch (C) (residual amounts) The masterbatch (C) was heated and melted at a temperature of melting point +20°C in a stainless steel circular ring with a thickness of 5 mm and an inner diameter of 50 mm to prepare a sample piece, and the amount of elements was determined by fluorescent X-ray analysis and expressed in ppm (by mass). Note that, when quantifying, a calibration curve obtained in advance from samples with known amounts of each element was used.

[0152] (13) Melting resistivity (ρi) Two electrodes (0.6 mm diameter stainless steel wires) were placed on both ends of the composition used to prepare the film of Example 11 (hereinafter referred to as the film-preparing composition), which was melted at 275°C. Two quartz plates, each 2 cm wide, sandwiched the composition and the two electrodes to form a uniform layer of the film-preparing composition 2 cm wide and 0.6 mm thick. A DC voltage of 120 V was applied at 280°C, and the current (io) was measured. This was then applied to the following equation to determine the melt resistivity ρi (Ω·cm). The melt resistivities of the film-preparing compositions, masterbatch (C), and composite masterbatch (D) of Examples 12 to 14 and Comparative Example 11 were also determined in the same manner. ρi(Ω·cm)=(A / L)×(V / io) [A: Electrode area (cm 2 ), L: distance between electrodes (cm), V: voltage (V), io: current (A)] A(cm 2 ) = [width of molten film-forming composition layer] × [thickness] = 2 (cm) × 0.06 (cm), and V = 120 (V). L is the value measured excluding the diameter of the electrodes, and is 1.3 cm.

[0153] (14) Electrostatic adhesion of film-forming compositions Using the film-making compositions of Examples 11 to 14 and Comparative Example 11, a tungsten wire electrode was placed between the extruder nozzle and the cooling drum, and a voltage of 10 to 15 kV was applied between the electrode and the casting drum to perform casting. The surface of the resulting cast raw sheet was observed with the naked eye and evaluated based on the casting speed at which pinner bubbles began to appear. The faster the casting speed, the better the electrostatic adhesion of the polymer.

[0154] (15) Static friction coefficient of polyester film (μs) Two polyester films of Example 11 were prepared, and one polyester film was bonded to the other polyester film in an environment of 23°C and 65% RH using a tensile tester (Tensilon RTG-1210 manufactured by A&D Co., Ltd.) in accordance with JIS K-7125. The static friction coefficient (μs) was determined when the polyester film was bonded to the other polyester film in accordance with JIS K-7125. The static friction coefficients of the films of Examples 12 to 14 and Comparative Example 11 were also determined in the same manner.

[0155] The preparation of the aluminum-containing ethylene glycol solution, the preparation of the phosphorus-containing ethylene glycol solution, and the production of the polyester resin (A), various masterbatches (B) to (D), and film will be described below.

[0156] (1) Preparation of aluminum-containing ethylene glycol solution a1 An equal volume (volume ratio) of ethylene glycol was added to a mixing tank and stirred at room temperature (23°C) for several hours. The mixture was then stirred under reduced pressure (3 kPa) at 50-90°C for several hours while distilling off water, producing an aluminum-containing ethylene glycol solution a1 containing 20 g / L of aluminum compounds. The maximum absorption wavelength of the aluminum-containing ethylene glycol solution a1 was 571.6 nm.

[0157] (2) Preparation of phosphorus-containing ethylene glycol solutions b1 and b1' <Phosphorus-containing ethylene glycol solution b1> Irganox 1222 (manufactured by BASF) was charged as a phosphorus compound into a mixing tank together with ethylene glycol, and the mixture was heated at 175°C for 150 minutes while stirring under nitrogen purging to prepare a phosphorus-containing ethylene glycol solution b1 containing 50 g / L of the phosphorus compound. The maximum absorption wavelength of the phosphorus-containing ethylene glycol solution b1 was 461.2 nm. <Phosphorus-containing ethylene glycol solution b1'> Phosphorus-containing ethylene glycol solution b1' was prepared in the same manner as phosphorus-containing ethylene glycol solution b1, except that the heat treatment conditions were changed to 80°C for 60 minutes. The maximum absorption wavelength of phosphorus-containing ethylene glycol solution b1' was 470.8 nm. The phosphorus-containing ethylene glycol solution b1' was used in Comparative Example 6, and in all Examples and Comparative Examples other than Comparative Example 6, the phosphorus-containing ethylene glycol solution b1 was used.

[0158] (3) Production of polyester resin (A) [Example of batch polymerization method] Example 1 A 10L stainless steel autoclave equipped with a stirrer was charged with a polyester oligomer with an esterification rate of approximately 95% consisting of high-purity terephthalic acid and ethylene glycol that had been previously mixed, and high-purity terephthalic acid, and an esterification reaction was carried out at 260°C to obtain an oligomer mixture. The resulting oligomer mixture had an acid end group concentration of 750 eq / ton and a hydroxyl end group ratio (OH%) of 59 mol%. To the resulting oligomer mixture, a one-component mixture of aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 prepared by the above method was added. The mixture was prepared so that the aluminum and phosphorus contents were 10 ppm by mass and 20 ppm by mass, respectively, relative to the mass of the oligomer mixture. The amount of polyester resin (A) produced can be calculated from the amount of terephthalic acid added. In this example, the mixture was added so that the aluminum and phosphorus contents were 10 ppm by mass and 20 ppm by mass, respectively, relative to the mass of the polyester resin produced. Thereafter, the temperature of the system was raised to 280°C over 1 hour, during which the pressure of the system was gradually reduced to 0.15 kPa, and under these conditions, a polycondensation reaction was carried out to obtain a polyester resin (A) having an IV of 0.60 dl / g.

[0159] (Examples 2 to 5, Comparative Examples 1 to 5) Polyester resin (A) was obtained in the same manner as in Example 1, except that aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 were added to the resulting polyester resin (A) so as to achieve the catalyst element addition amounts shown in Table 1.

[0160] (Comparative Example 6) Polyester resin (A) was obtained in the same manner as in Example 2, except that solution b1' was used as the phosphorus-containing ethylene glycol solution instead of solution b1.

[0161] The physical properties of the polyester resins (A) obtained in Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 1. In Table 1 and Table 2 described later, the added and remaining amounts of aluminum element are represented as Al, the added and remaining amounts of phosphorus element are represented as P, and the added and remaining molar ratio of phosphorus element to aluminum element is represented as P / Al.

[0162] [Table 1]

[0163] The polyester resins (A) of Examples 1 to 5 have short polymerization times and low amounts of aluminum and phosphorus, and therefore have low back pressure increase coefficients and high quality due to the low amounts of aluminum-based foreign matter. In addition, the catalyst addition amount is also small, which reduces the catalyst cost. Comparative Examples 1 and 2 have a high catalyst cost due to the large amount of phosphorus compound added, and a high molar ratio of added phosphorus element to aluminum element, which is preferable in that aluminum-based foreign matter is suppressed, but the polymerization activity is low. In Comparative Example 3, although the residual molar ratio of phosphorus element to aluminum element is within the range of the present invention, the amount of aluminum element added is too small, resulting in insufficient polymerization activity and a long polymerization time. In Comparative Examples 4 and 5, the residual molar ratio of phosphorus element to aluminum element was too low, so the amount of aluminum-based foreign matter in the polyester resin (A) increased, the back pressure increase coefficient was large, and the quality of the polyester resin (A) was poor. In Comparative Example 6, the molar ratio of phosphorus to aluminum added was within the range of the present invention, the polymerization time was short, and the catalyst cost was low. However, the maximum absorption wavelength of the phosphorus-containing ethylene glycol solution b1' was too long compared to Examples 1 to 5, so the remaining molar ratio of phosphorus to aluminum was low. In addition, the amount of aluminum-based foreign matter in the polyester resin (A) increased, which increased the back pressure increase coefficient, resulting in poor quality of the polyester resin (A).

[0164] [Example of continuous polymerization method] Example 6 A continuous polyester resin production apparatus was comprised of three continuous esterification reactors and three continuous polycondensation reactors, and an in-line mixer with a high-speed agitator was installed on the transfer line from the third esterification reactor to the first polycondensation reactor. A slurry prepared by mixing 1 part by mass of high-purity terephthalic acid with 0.75 parts by mass of ethylene glycol was continuously fed into the apparatus. The first esterification reactor was reacted at a temperature of 255°C and a pressure of 203 kPa, the second esterification reactor at a temperature of 261°C and a pressure of 102 kPa, and the third esterification reactor at a temperature of 261-263°C and a pressure of 126 kPa to produce an oligomer. The oligomer at the outlet of the third esterification reactor had an acid end group concentration of 550 eq / ton and a hydroxyl end group ratio (OH%) of 60 mol%. The resulting oligomer was mixed with the aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 prepared by the above method to form a one-component mixture, which was then added to the transfer line from the third esterification tank to the first polycondensation reactor using an in-line mixer. Specifically, the aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 prepared by the above method were used as catalysts, and the aluminum and phosphorus concentrations relative to the resulting oligomer were 13 ppm by mass and 36 ppm by mass, respectively, and the one-component solution was added. The amount of polyester resin (A) produced can be calculated from the amount of terephthalic acid added. In this example, the mixture was added so that the aluminum and phosphorus concentrations relative to the resulting polyester resin (A) were 13 ppm by mass and 36 ppm by mass, respectively. The oligomer-containing mixture was continuously transferred to a continuous polycondensation apparatus consisting of three reactors, and polycondensation was carried out at a reaction temperature of 268°C and a pressure of 5.3 kPa in the first polycondensation reactor, a reaction temperature of 270°C and a pressure of 0.930 kPa in the second polycondensation reactor, and a reaction temperature of 274°C and a pressure of 0.162 kPa in the third polycondensation reactor, yielding a polyester resin (A) with an IV of 0.59 dl / g. The polyester resin (A) was extruded into a strand, cooled in water, cut, and pelletized.

[0165] (Examples 7 and 8, Comparative Examples 7 and 8) Polyester resin (A) was obtained in the same manner as in Example 6, except that aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 were added to the obtained oligomer so as to achieve the catalyst element addition amounts shown in Table 2.

[0166] The physical properties of the polyester resins (A) obtained in Examples 6 to 8 and Comparative Examples 7 and 8 are shown in Table 2.

[0167] [Table 2]

[0168] The production volume ratios listed in Table 2 are expressed as ratios of the hourly production volumes of Examples 6 to 8 and Comparative Example 8, with the hourly production volume of Comparative Example 7 as the standard (the hourly production volume of Comparative Example 7 being 1.00). A production volume ratio higher than 1 indicates high polymerization activity of the catalyst, and conversely, a production volume ratio of 1 or less indicates low polymerization activity of the catalyst. The polyester resins (A) of Examples 6 to 8 had higher production ratios than those of Comparative Examples 7 and 8, and showed improved polymerization activity despite the small amounts of aluminum and phosphorus added. Furthermore, the amount of aluminum-based foreign matter in the polyester resins (A) was also small, so the back pressure increase coefficient was small, and high-quality polyester resins (A) were obtained. In Comparative Example 8, the residual molar ratio of phosphorus element to aluminum element was too low, so the amount of aluminum-based foreign matter in the polyester resin (A) increased, the back pressure increase coefficient increased, and the quality of the polyester resin (A) was poor.

[0169] Using the results of Examples 1 to 5 and Comparative Examples 1, 2, 4, and 5 in Table 1, the relationship between the residual molar ratio of phosphorus to aluminum, the amount of aluminum-based foreign matter, and the polymerization time is shown in Figure 1. Furthermore, the relationship between the maximum absorption wavelength of the mixed solution of aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1, the amount of aluminum-based foreign matter, and the polymerization time is shown in Figure 2. Furthermore, the relationship between the maximum absorption wavelength of the mixed solution of aluminum-containing ethylene glycol solution a1 and phosphorus-containing ethylene glycol solution b1 and the back pressure increase coefficient k is shown in Figure 3. In these figures, the values ​​for Comparative Example 3 are excluded. The reason is that although the molar ratio of the remaining phosphorus element to the aluminum element in Comparative Example 3 is within the range of the present invention, the amount of remaining aluminum is too small to fully exert catalytic activity, resulting in a lower polymerization activity than in the other cases.

[0170] These figures clearly show that the range of the present invention is critical. It is also clear that the amount of aluminum-based foreign matter and the polymerization time are trade-offs. Since the polyester resins (A) obtained in Examples 1 and 6 will be used below, the polyester resin (A) obtained in Example 1 will be referred to as polyester resin (A-1), and the polyester resin (A) obtained in Example 6 will be referred to as polyester resin (A-2).

[0171] (4) Production of antiblocking agent-containing masterbatch (B) [Example of polymerization process addition method] (Production Example 1-1) (i) Preparation of silica-containing ethylene glycol slurry Five liters of ethylene glycol and 600 g of silica particles (Fuji Silysia Chemical, Sylysia 310) with a volume average particle diameter of 2.4 μm as an antiblocking agent were placed in a dispersion tank equipped with a homogenizer, and the mixture was stirred and dispersed at 8000 rpm for 2 hours to produce a 120 g / L slurry.

[0172] (ii) Method for producing silica-containing masterbatch (B-1) A stainless steel autoclave equipped with a stirrer, distillation column, and pressure regulator was charged with 1297 parts by mass of high-purity terephthalic acid, 678 parts by mass of ethylene glycol, and the ethylene glycol slurry of silica particles prepared by the above method so that the SiO2 particles accounted for 0.7% by mass of the resulting polyester resin. 6 parts of triethylamine and 0.05 parts of sodium acetate were then added, and an esterification reaction was carried out according to a conventional method to obtain an oligomer mixture. The aluminum-containing ethylene glycol solution a1 and the phosphorus-containing ethylene glycol solution b1 prepared by the above method were added to this oligomer mixture in amounts of 40 ppm and 95 ppm of aluminum and phosphorus, respectively, relative to the mass of the resulting polyester resin. The temperature of the system was then raised to 280°C over 1 hour, during which the pressure of the system was gradually reduced to 0.15kPa, and a polycondensation reaction was carried out under these conditions to obtain a silica-containing masterbatch (B-1) with an IV of 0.59dL / g. The number of coarse particles in the obtained silica-containing masterbatch (B-1) was 68, and the silica-containing masterbatch (B-1) had a low number of coarse particles and was of high quality.

[0173] [Example of melt kneading method] (Production Example 1-2) Polyester resin (A-2) was blended with 90 parts by mass and 10 parts by mass of silica particles (Fuji Silysia Chemical, Sylysia 310) having a volume average particle size of 2.4 μm as an antiblocking agent, and then melt-kneaded at a cylinder temperature of 300°C using a twin-screw extruder (The Japan Steel Works, TEX30α) to obtain silica-containing masterbatch (B-2). The number of coarse particles in the obtained silica-containing masterbatch (B-2) was 120, and the silica-containing masterbatch (B-2) was of high quality with a small number of coarse particles.

[0174] (5) Manufacturing of single-layer polyester film (part 1) Example 9 A polyester resin composition obtained by mixing polyester resin (A-1) and silica-containing masterbatch (B-2) in a mass ratio of 98.8:1.2 was vacuum dried for 10 hours at 135°C. The mixture was then fed into a twin-screw extruder, extruded into a sheet at 280°C, and rapidly solidified on a metal roll whose surface temperature was maintained at 20°C to obtain a cast film with a thickness of 1400 μm. During the rapid solidification on the metal roll, adhesion to the metal roll was improved using an electrostatic adhesion device consisting of a sawtooth electrode. The cast film was then heated to 100°C using a group of heated rolls and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a group of rolls with different peripheral speeds to obtain a uniaxially oriented film. Subsequently, the film was stretched 4.0 times in the transverse direction at 120°C using a tenter. With the film width fixed, it was heated at 260°C for 0.5 seconds using an infrared heater, and then subjected to a 3% relaxation treatment at 200°C for 23 seconds to obtain a 100μm-thick biaxially oriented polyester film. The static friction coefficient (μs) of the obtained polyester film was 0.50, and it can be said that the film has good slip properties and excellent handling properties such as running properties, abrasion resistance, and winding properties.

[0175] Example 10 A biaxially oriented polyester film was produced in the same manner as in Example 9, except that polyester resin (A-2) was used instead of polyester resin (A-1). The static friction coefficient (μs) of the obtained polyester film was 0.50, indicating good slip properties and excellent handling properties such as running properties, abrasion resistance, and winding properties.

[0176] (Comparative Example 9) A biaxially oriented polyester film was produced in the same manner as in Example 9, except that the silica-containing masterbatch (B-2) was not mixed and only the polyester resin (A-1) was vacuum dried. The static friction coefficient (μs) of the obtained polyester film was 1 or more, and it can be said that the film had poor slip properties and poor handling properties such as running properties, abrasion resistance, and winding properties.

[0177] (Comparative Example 10) A biaxially oriented polyester film was produced in the same manner as in Example 10, except that the silica-containing masterbatch (B-2) was not mixed and only the polyester resin (A-2) was vacuum dried. The static friction coefficient (μs) of the obtained polyester film was 1 or more, and it can be said that the film had poor slip properties and poor handling properties such as running properties, abrasion resistance, and winding properties.

[0178] (6) Production of masterbatch (C) containing electrostatic adhesion promoter (Production Examples 2-1 to 2-5) High-purity terephthalic acid, ethylene glycol, and triethylamine were charged into a stainless steel autoclave equipped with a stirrer, distillation column, and pressure regulator, and an esterification reaction was carried out according to a conventional method to obtain an oligomer mixture. To this oligomer mixture, basic aluminum acetate, magnesium acetate dihydrate, potassium acetate, and triethyl phosphate were added so that the amounts of aluminum, magnesium, potassium, and phosphorus added were as shown in Table 3. Thereafter, the temperature of the system was raised to 280°C over 1 hour, during which the pressure of the system was gradually reduced to 0.15 kPa, and under these conditions, a polycondensation reaction was carried out for 80 minutes to obtain a masterbatch (C) containing an electrostatic adhesion imparting agent. The physical properties of the obtained electrostatic adhesion imparting agent-containing masterbatch (C) are shown in Table 3. Note that, hereinafter, the electrostatic adhesion imparting agent-containing masterbatch (C) produced in Production Example 2-1 will be referred to as electrostatic adhesion imparting agent-containing masterbatch (C-1), and the electrostatic adhesion imparting agent-containing masterbatch (C) produced in Production Example 2-2 will be referred to as electrostatic adhesion imparting agent-containing masterbatch (C-2).

[0179] [Table 3]

[0180] By setting the contents of magnesium, alkali metal, and phosphorus in the masterbatch (C) within the above-mentioned preferred ranges, the electrostatic adhesion-imparting agent-containing masterbatches (C-1) and (C-2) were able to suppress the coloring degree (Co-b) and increase the electrostatic adhesion (reduce the melt resistivity ρi).

[0181] (7) Production of monolayer polyester film (part 2) Example 11 The polyester resin (A-2), silica-containing masterbatch (B-1), and electrostatic adhesion-imparting agent-containing masterbatch (C-1) were mixed in the proportions shown in Table 4 and vacuum dried for 10 hours at 135°C. The mixture was then fed into a twin-screw extruder and extruded into a sheet at 280°C. The sheet was then rapidly cooled and solidified on a metal roll whose surface temperature was maintained at 20°C, yielding a cast film with a thickness of 1680 μm. The cast film was then heated to 100°C using a group of heated rolls and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a group of rolls with different peripheral speeds to obtain a uniaxially oriented film. Subsequently, the film was stretched 4.0 times in the transverse direction at 120°C using a tenter, and while the film width was fixed, it was heated at 260°C for 0.5 seconds using an infrared heater, and further relaxed at 200°C for 23 seconds by 3% to obtain a 12μm thick biaxially oriented polyester film.

[0182] Example 12 A biaxially oriented polyester film was produced in the same manner as in Example 11, except that the silica-containing masterbatch (B-2) was used instead of the silica-containing masterbatch (B-1) and the mixing ratio was changed to the ratio shown in Table 4.

[0183] (Comparative Example 11) A biaxially oriented polyester film was produced in the same manner as in Example 11, except that the silica-containing masterbatch (B-1) was not mixed and only the polyester resin (A-2) was used.

[0184] The physical properties of the polyester films obtained in Examples 11 and 12 and Comparative Example 11 are shown in Table 4.

[0185] [Table 4]

[0186] The polyester films of Examples 11 and 12 have excellent electrostatic adhesion, allowing for the production of films at an increased film production rate. The obtained polyester films of Examples 11 and 12 have excellent slip properties. On the other hand, the polyester film obtained in Comparative Example 11 was poor in both electrostatic adhesion and slipperiness, and was of low quality.

[0187] (8) Manufacture of composite masterbatch (D) (Production Example 3) A masterbatch (C) containing an electrostatic adhesion imparting agent was prepared in the same manner as in Production Example 2-1, except that in the polymerization method for the masterbatch (C) described in (6) above, an ethylene glycol slurry of silica particles prepared by the method described in (4) above was added in addition to high-purity terephthalic acid, ethylene glycol, and triethylamine so that the SiO2 particles accounted for 0.7 mass% of the mass of the resulting polyester resin. 8 A composite masterbatch (D-1) with a Ω·cm and Co-b of 15.8 was obtained. The number of coarse particles in the obtained composite masterbatch (D-1) was 81, and the quality was the same as that of Production Example 2-1.

[0188] (9) Manufacturing of three-layer polyester film Example 13 In Example 11, a biaxially oriented polyester film having a total thickness of 12 μm was produced in the same manner as in Example 11, except that the melt extrusion method was changed to a three-layer method having three extruders, the thickness ratio of surface layer / intermediate layer / surface layer was set to 0.11 / 0.78 / 0.11, the polyester resin composition of the surface layer was the same as in Example 11, and the polyester resin composition of the intermediate layer was set to polyester resin (A-2) / electrostatic adhesion-imparting agent-containing masterbatch (C-1) = 95 / 5 (mass ratio). The obtained polyester film had the same productivity and slipperiness as the polyester film obtained in Example 11, and was visually evaluated to have excellent transparency.

[0189] Example 14 A biaxially stretched polyester film having a total thickness of 12 μm was obtained in the same manner as in Example 13, except that the polyester resin composition for the surface layer was polyester resin (A-2) / composite masterbatch (D-1)=95 / 5 (mass ratio). The obtained polyester film had the same productivity and slipperiness as the polyester film obtained in Example 11, and was visually evaluated to have excellent transparency.

[0190] The physical properties of the polyester films obtained in Examples 13 and 14 are shown in Table 5.

[0191] [Table 5] [Industrial Applicability]

[0192] The polyester resin composition obtained by the production method of the present invention can improve productivity of the polyester resin composition while keeping catalyst costs low, which has been an issue with polyester resin compositions obtained using a polymerization catalyst comprising an aluminum compound and a phosphorus compound, and can reduce catalyst-derived contaminants contained in the polyester resin composition, thereby providing a clean, high-quality polyester resin composition. In addition, polyester films produced using the polyester resin composition have slip properties. Furthermore, by forming a film from the polyester resin composition containing an electrostatic adhesion imparting agent, the melt resistivity can be sufficiently reduced. Furthermore, when the polyester resin composition containing a masterbatch containing little foreign matter and excellent color tone and thermal stability is used, film-forming properties can be improved and a polyester film with excellent quality can be produced. Therefore, polyester films produced using the polyester resin composition of the present invention can be used in a wide range of applications, including, for example, antistatic films, easy-adhesion films, cards, dummy cans, agricultural applications, building materials, decorative materials, wallpaper, overhead projector films, printing, inkjet recording, sublimation transfer recording, laser beam printer recording, electrophotographic recording, thermal transfer recording, thermal transfer recording, printed circuit board wiring, membrane switches, near-infrared absorbing films for plasma displays, transparent conductive films for touch panels and electroluminescence, masking films, photoengraving, X-ray films, photographic negative films, retardation films, polarizing films, polarizing film protectors (TAC), protective films and / or separator films for inspecting polarizing plates and retardation plates, photosensitive resin films, field of view expansion films, diffusion sheets, reflective films, anti-reflection films, UV protection, and backgrinding tapes.

Claims

1. The method includes a step of mixing a base polyester resin (A) containing an aluminum compound and a phosphorus compound and satisfying the following (1) to (3) with a masterbatch (B) containing an antiblocking agent, The method for producing a polyester resin composition, wherein the phosphorus compound is heat-treated in an alkylene glycol solution at 170 to 196°C. (1) The aluminum element content in the base polyester resin (A) is 9 to 19 ppm by mass. (2) The content of phosphorus element in the base polyester resin (A) is 13 to 31 mass ppm. (3) The molar ratio of phosphorus element to aluminum element in the base polyester resin (A) is 1.32 or more and 1.80 or less.

2. 2. The method for producing a polyester resin composition according to claim 1, wherein the masterbatch (B) contains insoluble particles that are insoluble in the base polyester resin (A), the insoluble particles have a volume average particle diameter of 0.5 to 3.0 μm, and the content of the insoluble particles is 0.5 to 20 mass%.

3. The method for producing a polyester resin composition according to claim 1 or 2, further comprising mixing a masterbatch (C) containing an electrostatic adhesion imparting agent.

4. 4. The method for producing a polyester resin composition according to claim 3, wherein the masterbatch (C) is a polyester resin containing a magnesium compound, an alkali metal compound, and a phosphorus compound, and the masterbatch (C) contains 400 to 2700 ppm by mass of magnesium element, 40 to 270 ppm by mass of alkali metal element, and 200 to 1700 ppm by mass of phosphorus element.

5. 3. The method for producing a polyester resin composition according to claim 1, wherein a masterbatch (D) containing an antiblocking agent and an electrostatic adhesion imparting agent is mixed with the base polyester resin (A) in place of the masterbatch (B).

6. 6. The method for producing a polyester resin composition according to claim 5, wherein the masterbatch (D) contains insoluble particles that are insoluble in the base polyester resin (A), the insoluble particles having a volume average particle diameter of 0.5 to 3.0 μm and a content of the insoluble particles of 0.5 to 20 mass %, and further contains 400 to 2700 ppm by mass of magnesium element, 40 to 270 ppm by mass of alkali metal element, and 200 to 1700 ppm by mass of phosphorus element.

7. The method for producing a polyester resin composition according to claim 4 or 6, wherein the alkali metal contained in the masterbatch (C) or the masterbatch (D) is potassium.

8. 8. The method for producing a polyester resin composition according to claim 4, 6, or 7, wherein the phosphorus compound contained in the masterbatch (C) or the masterbatch (D) is a trialkyl phosphate, and at least one of the alkyl groups of the trialkyl phosphate is an alkyl group having 2 to 4 carbon atoms.

9. The method for producing a polyester resin composition according to claim 8, wherein the phosphorus compound contained in the masterbatch (C) or the masterbatch (D) is triethyl phosphate.

10. The melt resistivity of the masterbatch (C) or the masterbatch (D) is 0.005×10 8 ~0.05 x 10 8 The method for producing a polyester resin composition according to any one of claims 3 to 9, wherein the viscosity is Ω·cm.

11. The method for producing a polyester resin composition according to any one of claims 3 to 10, wherein the masterbatch (C) or the masterbatch (D) is a polyester containing a dicarboxylic acid component and a glycol component as constituent components, and satisfies the following (4), where m (mol %) is the amount of magnesium element, k (mol %) is the amount of alkali metal element, and p (mol %) is the amount of phosphorus element relative to the dicarboxylic acid component: (4) 2≦(m+k / 2) / p≦3.5

12. 12. The method for producing a polyester resin composition according to claim 1, wherein the phosphorus compound contained in the base polyester resin (A) has a phosphorus element and a phenol structure in the same molecule.

13. The method for producing a polyester resin composition according to any one of claims 1 to 12, wherein the content of aluminum element corresponding to aluminum-based foreign matter in the base polyester resin (A) is 3000 mass ppm or less.

14. The method for producing a polyester resin composition according to any one of claims 1 to 13, wherein the base polyester resin (A) has an intrinsic viscosity (IV) of 0.56 dl / g or more.

15. A method for producing a polyester resin described in any of claims 1 to 14, wherein the base polyester resin (A) contains a substance derived from a polymerization catalyst, and the polymerization catalyst contains only a polymerization catalyst consisting of an aluminum compound and a phosphorus compound.

16. The method for producing the base polyester resin (A) includes a first step of synthesizing a polyester or an oligomer thereof as a polycondensation product as an intermediate, and a second step of further polycondensing the intermediate, 16. The method for producing a polyester resin composition according to any one of claims 1 to 15, wherein a solution A1 in which an aluminum compound is dissolved and a solution B1 in which a phosphorus compound is dissolved are added to the intermediate after the first step and before the second step, and the amounts of the solution A1 and the solution B1 added satisfy the following (5) to (7): (5) The amount of aluminum element added to the base polyester resin (A) produced is 9 to 19 mass ppm. (6) The amount of phosphorus added to the base polyester resin (A) produced is 18 to 38 mass ppm. (7) The molar ratio of the amount of added phosphorus element in (6) to the amount of added aluminum element in (5) is 1.50 or more and 2.30 or less.

17. The method for producing a polyester resin composition according to claim 16, wherein the base polyester resin (A) is produced by a batch polymerization method.

18. 17. The method for producing a polyester resin composition according to claim 16, wherein the base polyester resin (A) is produced by a continuous polymerization method, and the solution A1 and the solution B1 are added to a final esterification reaction tank or to a transfer line between the final esterification reaction tank and a first polymerization reaction tank.

19. The method for producing a polyester resin composition according to any one of claims 16 to 18, wherein the solution A1 is a glycol solution, and the maximum absorption wavelength of the solution A1 is 562.0 to 572.0 nm.

20. 20. The method for producing a polyester resin composition according to claim 19, wherein the solution B1 is a glycol solution, and the maximum absorption wavelength of the solution B1 is 458.0 to 465.0 nm.

21. The method for producing a polyester resin composition according to any one of claims 16 to 20, wherein the solution A1 and the solution B1 are glycol solutions, and the maximum absorption wavelength of a mixed solution of the glycol solution A1 and the glycol solution B1 is 559.5 to 560.8 nm.

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