Polyester resin, hollow molded body molded therefrom, and method for manufacturing the same

Abstract

A polyester resin reduced in the contents of a cyclic trimer and an aluminum-based foreign matter and a blow-molded object are provided, with maintained catalytic activity and a reduced catalyst cost. The polyester resin contains an aluminum compound and a phosphorus compound and is characterized by satisfying the following (1) to (3).　(1) To have an aluminum element content of 9-19 mass ppm (2) To have a phosphorus element content of 22-40 mass ppm (3) To have a molar ratio of phosphorus element to aluminum element of 1.55-1.85

Description

[Technical Field]

[0001] The present invention relates to a polyester resin, a blown molded article molded therefrom, and a method for producing the same. The polyester resin and the blown molded article molded therefrom contain catalytic amounts of a component derived from an aluminum compound and a component derived from a phosphorus compound, thereby reducing the amounts of cyclic trimer and aluminum-based foreign matter in the polyester resin and the blown molded article, and achieving both improved quality such as thermal stability and reduced catalyst costs. [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 applications, depending on the properties of each polyester resin, including fibers for clothing and industrial materials, films and sheets for packaging, magnetic tape, and optical applications, blown-molded bottles, casings for electrical and electronic components, and other engineering plastic molded products. In particular, bottles made from saturated polyester resins such as PET are widely used as containers for filling beverages such as juices, carbonated drinks, and soft drinks, as well as for eye drops and cosmetics, due to their excellent mechanical strength, heat resistance, transparency, and gas barrier properties.

[0003] A typical polyester resin, whose main components are units derived from aromatic dicarboxylic acids and alkylene glycols, is produced by, for example, PET, producing an oligomer mixture such as bis(2-hydroxyethyl) terephthalate through an esterification reaction or transesterification reaction between terephthalic acid or dimethyl terephthalate and ethylene glycol, and then melt-polymerizing this mixture at high temperature in a vacuum using a catalyst.

[0004] Antimony compounds or germanium compounds have been widely used as polyester polymerization catalysts for polymerizing such 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 are completely free of antimony or that do not contain antimony 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 compounds or germanium compounds, and titanium compounds, such as tetraalkoxy titanates, have already been proposed. However, 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] As a novel polymerization catalyst, a catalyst system comprising an aluminum compound and a phosphorus compound has been disclosed and has attracted attention (see, for example, Patent Documents 1 and 2). The use of the above polymerization catalyst makes it possible to obtain polyester resins with good color tone, transparency, and thermal stability. However, this method has the problem of high catalyst cost due to the large amount of catalyst added and the high cost of the phosphorus compound used. Furthermore, in order to obtain a high-quality polyester resin while maintaining high polymerization activity, it is necessary to increase the amounts of aluminum compounds and phosphorus compounds added as catalysts, which results in an increase in catalyst costs. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] International Publication No. 2007 / 032325 Brochure [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-169432 Summary of the Invention [Problem to be solved by the invention]

[0010] The present invention has been made in view of the problems of the prior art as described above, and aims to provide a polyester resin and a blow molded article which, despite using a polymerization catalyst comprising an aluminum compound and a phosphorus compound, the main metal component of which is a metal component other than antimony, germanium, and titanium, maintains polymerization activity while reducing catalyst costs and which contain little cyclic trimer and aluminum-based foreign matter. [Means for solving the problem]

[0011] As a result of extensive research to solve the above-mentioned problems, the present inventors have found that the object can be achieved by reducing the amount of aluminum element contained in a polyester resin and adjusting the molar ratio of phosphorus element to aluminum element within an appropriate range, and have 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.

[0012] 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 a polyester resin and adjusting the molar ratio of phosphorus element to aluminum element within an appropriate range, it is possible to reduce the amount of cyclic trimer and aluminum-based foreign matter in the polyester resin while achieving excellent polymerization activity and suppressing catalyst costs, thereby completing the present invention.

[0013] That is, the present invention comprises the following configurations. [1] A polyester resin containing an aluminum compound and a phosphorus compound, characterized in that the polyester resin satisfies the following (1) to (3): (1) The content of aluminum element in the polyester resin is 9 to 19 mass ppm. (2) The content of phosphorus element in the polyester resin is 22 to 40 mass ppm. (3) The molar ratio of phosphorus to aluminum in the polyester resin is 1.55 or more and 1.85 or less. [2] The polyester resin according to [1], wherein the content of aluminum elements corresponding to aluminum-based foreign matter in the polyester resin is 1650 mass ppm or less. [3] The polyester resin according to [1] or [2] above, which has an intrinsic viscosity (IV) of 0.56 dl / g or more. [4] The polyester resin according to any one of [1] to [3], wherein the phosphorus compound has a phosphorus element and a phenol structure in the same molecule. [5] The polyester resin according to any one of [1] to [4] above, wherein the amount of cyclic trimer is 5000 ppm or less. [6] A method for producing a polyester resin according to any one of [1] to [5] above, A first step of synthesizing a polyester or an oligomer thereof as a polycondensate as an intermediate; a second step of melt polymerizing the intermediate; and a third step of solid-state polymerizing the melt-polymerized polyester, A method for producing a polyester resin, comprising adding 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, and adding the solution A1 and the solution B1 in amounts that satisfy the following (4) to (6): (4) The amount of aluminum element added to the polyester resin to be produced is 9 to 19 ppm by mass. (5) The amount of phosphorus added to the polyester resin to be produced is 25 to 50 mass ppm. (6) The molar ratio of the amount of added phosphorus element in (5) to the amount of added aluminum element in (4) is 2.00 or more and 2.40 or less. [7] The method for producing a polyester resin according to [6], wherein the melt polymerization is carried out until the intrinsic viscosity (IV) reaches 0.56 to 0.65 dL / g, and then the solid-state polymerization is carried out until the intrinsic viscosity (IV) reaches 0.70 to 0.85 dL / g. [8] The method for producing a polyester resin according to [6] or [7], wherein the solution A1 is a glycol solution, and the maximum absorption wavelength of the solution A1 is 562.0 to 572.0 nm. [9] The method for producing a polyester resin according to [8], wherein the solution B1 is a glycol solution, and the solution B1 has a maximum absorption wavelength of 460.0 to 463.0 nm.

[10] The method for producing a polyester resin according to [9], wherein the glycol solution B1 is a glycol solution in which a phosphorus compound is heat-treated at 170 to 196°C for 125 to 240 minutes.

[11] The method for producing a polyester resin according to any one of [6] to

[10] above, 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.

[12] A hollow molded article formed from a polyester resin containing an aluminum compound and a phosphorus compound, characterized in that the hollow molded article satisfies the following (7) to (9): (7) The aluminum element content in the hollow molded body is 9 to 19 ppm by mass. (8) The phosphorus content in the hollow molded body is 22 to 40 mass ppm. (9) The molar ratio of phosphorus element to aluminum element in the hollow molded body is 1.55 or more and 1.85 or less.

[13] The hollow molded body according to

[12] , wherein the content of aluminum element corresponding to aluminum-based foreign matter in the hollow molded body is 1650 mass ppm or less.

[14] The blown molded article according to

[12] or

[13] , wherein the phosphorus compound has a phosphorus element and a phenol structure in the same molecule.

[15] The blow molded article according to any one of

[12] to

[14] , wherein the amount of cyclic trimer is 6000 ppm or less.

[16] A method for producing the hollow molded article according to any one of

[12] to

[15] above, characterized in that the hollow molded article is produced by molding the polyester resin according to any one of [1] to [5] above. [Effects of the Invention]

[0014] The polyester resin of the present invention is a polyester resin obtained using a polymerization catalyst composed of an aluminum compound and a phosphorus compound, the main metal component of which is a metal component other than antimony, germanium, and titanium. The polyester resin has good color tone and thermal stability, and the production of cyclic trimers and aluminum-based foreign matter is suppressed while maintaining polymerization activity. Furthermore, the high catalyst cost, which is one of the problems associated with the production of polyester resins using a polymerization catalyst composed of an aluminum compound and a phosphorus compound, can be improved. The blown molded article of the present invention is molded from a polyester resin obtained using a polymerization catalyst composed of an aluminum compound and a phosphorus compound, the main metal component of which is a metal component other than antimony, germanium, and titanium. The blown molded article of the present invention not only has a good color tone and thermal stability, but also suppresses the formation of cyclic trimers and aluminum-based foreign matter while maintaining polymerization activity. Furthermore, the high catalyst cost, which is one of the problems associated with the production of polyester resins using a polymerization catalyst composed of an aluminum compound and a phosphorus compound, can be improved. [Brief explanation of the drawings]

[0015] [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. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention will be described in detail below.

[0017] The polyester resin of the present invention contains an aluminum compound and a phosphorus compound, and satisfies the following (1) to (3): (1) The content of aluminum element in the polyester resin is 9 to 19 mass ppm. (2) The content of phosphorus element in the polyester resin is 22 to 40 mass ppm. (3) The molar ratio of phosphorus to aluminum in the polyester resin is 1.55 or more and 1.85 or less. In this specification, ppm by mass is 10 -4 The percentages represent mass %.

[0018] The polyester resin of the present invention includes a polyester resin comprising 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.

[0019] In the polyester resin of the present invention, the main polycarboxylic acid component is preferably a dicarboxylic acid.

[0020] The polyester resin 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.

[0021] 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;

[0022] 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.

[0023] A polyester resin 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Examples of the ester-forming derivatives of polycarboxylic acids or hydroxycarboxylic acids include alkyl esters, acid chlorides, and acid anhydrides thereof.

[0028] In the polyester resin of the present invention, the main polyhydric alcohol component is preferably glycol.

[0029] The polyester resin containing glycol as the main polyhydric alcohol component is preferably a polyester resin containing glycol in an amount of 70 mol % or more, more preferably 80 mol % or more, and even more preferably 90 mol % or more, based on the total polyhydric alcohol components. When two or more glycols are used, the total amount is preferably within the above range.

[0030] 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.

[0031] 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.

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] The polyester resin of the present invention 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 of the present invention 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.

[0037] In the case of a hollow molded article that requires transparency, the above-mentioned copolymer of ethylene terephthalate and at least one of the above-mentioned monomers other than ethylene terephthalate may be a copolymer obtained by copolymerizing isophthalic acid, neopentyl glycol, 1,4-cyclohexanedimethanol, polyethylene glycol, or the like, which are copolymerization components that can reduce the crystallinity of the polyester.

[0038] <Polymerization catalyst> The polyester resin of the present invention contains catalytic amounts of a component derived from an aluminum compound and a component derived from a phosphorus compound, i.e., the polyester resin of the present invention is produced using a polymerization catalyst comprising an aluminum compound and a phosphorus compound.

[0039] <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.

[0040] 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 demonstrate the effects of the present invention.

[0041] The aluminum element content in the polyester resin of the present invention 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 element content is less than 9 ppm by mass, the polymerization activity may not be fully exerted. On the other hand, if the aluminum element content exceeds 19 ppm by mass, the amount of aluminum-based foreign matter may increase and the cost of the catalyst may increase, which is not preferable.

[0042] <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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] [ka]

[0047] (In (Chemical Formula 1), X 1 , X 2 respectively represent hydrogen and an alkyl group having 1 to 4 carbon atoms.

[0048] 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.

[0049] 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.

[0050] The phosphorus content in the polyester resin of the present invention is 22 to 40 ppm by mass, preferably 23 to 35 ppm by mass, and more preferably 24 to 32 ppm by mass. If the phosphorus content is less than 22 ppm by mass, the catalytic activity may not be fully exerted and the amount of aluminum-based foreign matter and cyclic trimer may increase. On the other hand, if the phosphorus content exceeds 40 ppm by mass, the polymerization activity may decrease and the amount of phosphorus compound added may increase, resulting in increased catalyst costs.

[0051] <Mole ratio of phosphorus element to aluminum element in polyester resin> In the polyester resin of the present invention, 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 1.55 to 1.85, preferably 1.57 to 1.82, and more preferably 1.59 to 1.77. As described above, the aluminum and phosphorus in the polyester resin of the present invention are derived from the aluminum compound and phosphorus compound used as polymerization catalysts for the polyester resin, 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, thereby achieving sufficient polymerization activity. If the residual molar ratio of phosphorus to aluminum is less than 1.55, the thermal stability and thermo-oxidative stability may be reduced, which may result in severe coloration of the polyester resin and an increase in the amount of aluminum-based foreign matter and cyclic trimer. On the other hand, if the residual molar ratio of phosphorus to aluminum exceeds 1.85, the polymerization activity may be reduced and the catalyst cost may increase due to the addition of too much phosphorus compound.

[0052] 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 obtained by the production method of the present invention. The content of antimony element in the polyester resin is preferably 30 ppm by mass or less, the content of germanium element in the polyester resin is preferably 10 ppm by mass or less, and the content of titanium element in the polyester resin 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.

[0053] The polyester resin of the present invention preferably has an aluminum element content, corresponding to aluminum-based foreign matter, of 1650 ppm by mass or less, more preferably 1200 ppm by mass or less, even more preferably 1100 ppm by mass or less, and even more preferably 1000 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 of the present invention. If the aluminum-based foreign matter content exceeds the above range, fine foreign matter insoluble in the polyester resin may cause deterioration in the quality of fibers, films, molded products, etc. This may also lead to issues such as increased filter clogging during polyester filtration in the polycondensation process and film-forming process. The lower limit of the aluminum element content, corresponding to aluminum-based foreign matter, is preferably 0 ppm by mass, but is set to approximately 200 ppm by mass due to technical difficulties. As can be seen from the fact that the amount of aluminum element is measured by the measurement method described later in the Examples section of this specification, 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.

[0054] The intrinsic viscosity (IV) of the polyester resin of the present invention is preferably 0.56 dL / g or more, more preferably 0.65 to 0.80 dL / g, and even more preferably 0.70 to 0.75 dL / g. If the intrinsic viscosity of the polyester resin 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 exceeds the above range, economic efficiency decreases, which is not preferable.

[0055] The content of cyclic trimer (CT) in the polyester resin of the present invention is preferably 5000 mass ppm or less, more preferably 4500 mass ppm. Although there is no particular lower limit, it is preferably 2700 mass ppm or more from the viewpoint of technical difficulties. If the content of cyclic trimer exceeds 5000 mass ppm, there is a risk of increased mold fouling during molding.

[0056] [Method of producing polyester resin of the present invention] The method for producing the polyester resin of the present invention can be carried out by a method including known steps, except that a polyester polymerization catalyst comprising an aluminum compound and a phosphorus compound is used as the catalyst and that the polymerization catalyst is added so as to satisfy the following (4) to (6).

[0057] The method for producing the polyester resin of the present invention 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, and more preferably comprises a third step of solid-state polymerizing the melt-polymerized polyester after the first step and the second step.

[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 following (4) to (6): The polycarboxylic acids and their ester-forming derivatives, the hydroxycarboxylic acids and their ester-forming derivatives which may be added in small amounts, and the cyclic esters which may be added in small amounts, all of which are used in the production of the polyester resin of the present invention, 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 produced by polymerization; therefore, the mass of the "polyester resin produced" can be calculated from the amounts of these ingredients charged. (4) The amount of aluminum element added to the polyester resin to be produced is 9 to 19 ppm by mass. (5) The amount of phosphorus added to the polyester resin to be produced is 25 to 50 mass ppm. (6) The molar ratio of the amount of phosphorus added in (5) to the amount of aluminum added in (4) (hereinafter referred to as "molar ratio of phosphorus added to aluminum") is 2.00 or more and 2.40 or less.

[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 method for producing the polyester resin of the present invention can be carried out by a method including conventionally known steps, except that a polyester polymerization catalyst composed of an aluminum compound and a phosphorus compound is used as a catalyst, and the aluminum content, phosphorus content, and molar ratio of phosphorus to aluminum in the polyester resin of the present invention are adjusted to fall within specific ranges. For example, polyethylene terephthalate can be produced by a direct esterification method in which terephthalic acid and ethylene glycol, and optionally other copolymerization components, are directly reacted, water is distilled off, esterification is performed, and polycondensation is then carried out under atmospheric or reduced pressure. Alternatively, dimethyl terephthalate and ethylene glycol, and optionally other copolymerization components, methyl alcohol is distilled off, transesterification is performed, and polycondensation is then carried out under atmospheric or reduced pressure. Melt polymerization can be either a batch polymerization method or a continuous polymerization method. Solid-state polymerization is not required, but is preferred. If solid-state polymerization is carried out, the melt-polymerized polyester can be allowed to absorb moisture and then heated to crystallize, or water vapor can be directly sprayed onto polyester chips to heat crystallize, in order to promote crystallization before solid-state polymerization. The amount (mass) of the polyester resin produced can be calculated from the amount (mass) of the polycarboxylic acid including the dicarboxylic acid used as a raw material.

[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 of the present invention is produced by multi-stage esterification reaction or transesterification reaction and continuous polymerization, it is preferable to add solution A1 in which an aluminum compound is dissolved and solution B1 in which a 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] 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 later stage), it is preferable that the first stage is the initial stage, the final stage is the later stage, and the stages from the second stage to the stage just before the final stage are the middle stage, and the reaction conditions for the polymerization reaction in the middle stage are between those in the initial stage and those in the later stage. It is preferable that the degree of increase in intrinsic viscosity achieved in each of these polymerization reaction steps is smoothly distributed.

[0063] <Solid phase polymerization method> In order to increase the intrinsic viscosity, the polyester resin produced by the melt polymerization method may be subjected to solid-state polymerization. The solid-state polymerization may be a batch polymerization method or a continuous polymerization method, but it is preferable to carry out the solid-state polymerization in a continuous apparatus, as in the melt polymerization.

[0064] In the present invention, a preferred method for reducing the CT amount is to additionally polymerize a polyester resin produced by melt polymerization using solid-state polymerization. Solid-state polymerization is carried out by converting the polyester obtained in the second step (melt polymerization) into a powder or granular form. The powder or granular form refers to polyester in chip, pellet, flake, or powder form, with chip or pellet being preferred.

[0065] The solid-state polymerization is carried out by heating the granular polyester at a temperature below the melting point of the polyester in an inert gas stream or under reduced pressure. The solid-state polymerization process may be carried out in one stage or in multiple stages.

[0066] The particulate polyester to be supplied to the solid-phase polymerization step may be pre-crystallized by heating it to a temperature lower than the temperature at which solid-phase polymerization is carried out, and then supplied to the solid-phase polymerization step.

[0067] Such a pre-crystallization step may be carried out by heating the granular polyester in a dry state at a temperature of usually 120 to 200°C, preferably 130 to 180°C, for 1 minute to 4 hours, or by heating the granular polyester in a water vapor atmosphere, a water vapor-containing inert gas atmosphere, or a water vapor-containing air atmosphere at a temperature of usually 120 to 200°C for 1 minute or more.

[0068] The polyester melt-polymerized as described above is, for example, chipped and then transported through a transport pipeline to a storage silo or a solid-state polymerization process. If such chips are transported using a forced low-density transport method, for example, using air, the surface of the melt-polymerized polyester chips is subjected to a large impact force when it collides with the pipeline, resulting in the generation of large amounts of fines and film-like substances. Such fines and film-like substances have the effect of promoting the crystallization of the polyester, and if present in large amounts, the transparency of the resulting molded product will be significantly reduced. Therefore, adding a process for removing such fines and film-like substances is one preferred embodiment.

[0069] The method for removing the fines and film-like substances is not limited, but examples thereof include a method of treating the fines and film-like substances using a vibrating sieve process, an air current classification process using an air current, a gravity classification process, etc., which are separately installed as an intermediate process between the solid-state polymerization process and a subsequent process installed after the solid-state polymerization process.

[0070] <Physical properties of intermediates> 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.

[0071] 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.

[0072] In the method for producing a polyester resin of the present invention, it is preferable to carry out melt polymerization until the intrinsic viscosity reaches 0.56 to 0.65 dL / g, followed by solid-state polymerization until the intrinsic viscosity reaches 0.70 to 0.85 dL / g, and more preferably to carry out melt polymerization until the intrinsic viscosity reaches 0.58 to 0.62 dL / g, followed by solid-state polymerization until the intrinsic viscosity reaches 0.70 to 0.75 dL / g. If the intrinsic viscosity after melt polymerization is less than 0.56 dL / g, friction between the polyester resin pellets and the pneumatic transport piping may cause a large amount of fines to be generated during pneumatic transport of the polyester resin. On the other hand, if the intrinsic viscosity after melt polymerization exceeds 0.65 dL / g, economic efficiency may decrease. If the intrinsic viscosity after solid-state polymerization is less than 0.70 dL / g, the CT amount may not be reduced sufficiently and the moldability of the hollow molded body may deteriorate. On the other hand, if the intrinsic viscosity after solid-state polymerization exceeds 0.85 dL / g, injection molding into a bottomed preform may become difficult.

[0073] 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.

[0074] In the present invention, after the esterification reaction or transesterification reaction is completed, it is preferable to add solution A1 in which an aluminum compound is dissolved and solution B1 in which a phosphorus compound is dissolved so that the contents (residual amounts) of aluminum element and phosphorus element in the polyester resin fall within the ranges that satisfy the above (1) to (3).

[0075] 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 the polyester resin 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.

[0076] Furthermore, even if the aluminum compound functioning as a catalyst is placed in a reduced pressure environment during polymerization of the polyester resin, almost 100% of the amount initially added to the system as a catalyst remains in the polyester resin produced by polymerization. In other words, since the amount of aluminum compound remains almost unchanged before and after polycondensation, if the amount of aluminum added to the intermediate is 9 to 19 ppm by mass, the content of aluminum in the polyester resin will also be 9 to 19 ppm by mass.

[0077] Furthermore, when the phosphorus compound, which functions as a catalyst together with the aluminum compound, is placed in a reduced pressure environment during polyester resin polymerization, 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 that is the final product satisfies the above (2).

[0078] 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.

[0079] When the polyester resin of the present invention 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).

[0080] 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.

[0081] <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 569.0 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.

[0082] 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.

[0083] 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.

[0084] 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.

[0085] <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.

[0086] 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.

[0087] 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.

[0088] <Heat treatment of phosphorus compounds> Furthermore, the phosphorus compound used in the present invention is preferably heat-treated in a solvent. The solvent used is not limited as long as it is at least one selected from the group consisting of water and alkylene glycol, but 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 polyester resin of the present invention, such as ethylene glycol. The heat treatment in the solvent is preferably carried out after the phosphorus compound has been dissolved, but it is not necessary for the phosphorus compound to be completely dissolved.

[0089] 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.

[0090] The concentration of the phosphorus compound during the heat treatment is preferably 3 to 10% by mass.

[0091] 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.

[0092] 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.

[0093] [ka]

[0094] 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.

[0095] <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.

[0096] 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.

[0097] [Molded body] The polyester resin of the present invention can be molded into hollow molded articles, films, sheets, fibers, and other molded articles using a commonly used melt molding method, and can also be molded into coated articles on other substrates using a melt extrusion method. The mechanical strength of the sheet-like material made of the polyester resin of the present invention can be improved by stretching it at least uniaxially. The stretched film made of the polyester resin of the present invention is formed by molding a sheet-like product obtained by injection molding or extrusion molding into a cup-like or tray-like shape by any stretching method commonly used for stretching PET, including uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching. It can also be formed into a cup-like or tray-like shape by pressure forming or vacuum forming.

[0098] In particular, the polyester resin of the present invention is suitably used as a blow molded article.

[0099] <Hollow molded body> The blow molded article of the present invention is molded from a polyester resin containing an aluminum compound and a phosphorus compound, and is preferably formed from the above-mentioned polyester resin of the present invention.

[0100] The hollow molded body satisfies the following (7) to (9). (7) The aluminum element content in the hollow molded body is 9 to 19 ppm by mass. (8) The phosphorus content in the hollow molded body is 22 to 40 mass ppm. (9) The molar ratio of phosphorus element to aluminum element in the hollow molded body is 1.55 or more and 1.85 or less.

[0101] In the process of molding the hollow molded body, the aluminum element content, phosphorus element content, and aluminum element content corresponding to aluminum-based foreign matter do not change. That is, the hollow molded body and the polyester resin used to mold the hollow molded body have the same aluminum element content, phosphorus element content, and aluminum element content corresponding to aluminum-based foreign matter. It is preferable that various physical properties of the hollow molded body, such as the aluminum element content, phosphorus element content, residual molar ratio of phosphorus to aluminum element, and aluminum element content corresponding to aluminum-based foreign matter, are within the suitable ranges for the polyester resin of the present invention described above.

[0102] However, the amount of cyclic trimer (CT) increases during the molding process of the hollow molded body. Therefore, the content of cyclic trimer in the hollow molded body of the present invention is preferably 6000 ppm by mass or less, more preferably 5500 ppm by mass or less. Although a lower content of cyclic trimer in the hollow molded body is preferable, due to technical difficulties, the limit is approximately 3000 ppm by mass. If the CT content of the hollow molded body is high, the mold surface may be contaminated. If the contamination accumulates on the mold surface with repeated molding, the resulting hollow molded body may become cloudy. To avoid these problems, the mold cleaning cycle must be increased, resulting in reduced productivity.

[0103] This application claims the benefit of priority to Japanese Patent Application No. 2020-156455, filed on September 17, 2020. The entire content of the specification of Japanese Patent Application No. 2020-156455, filed on September 17, 2020, is incorporated herein by reference. [Example]

[0104] 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.

[0105] [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

[0106] (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'.

[0107] (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

[0108] (4) Intrinsic viscosity (IV) of polyester resin The polyester resins after melt polymerization and solid phase polymerization were each dissolved in a mixed solvent of p-chlorophenol / 1,1,2,2-tetrachloroethane (=3 / 1; mass ratio), and the measurement was carried out at a temperature of 30°C.

[0109] (5) Aluminum content in polyester resin Polyester resin 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 after solid-state polymerization was determined using inductively coupled plasma atomic 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

[0110] (6) Phosphorus content in polyester resin The polyester resin after solid-state polymerization 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 the polyester resin after solid-state polymerization was determined from a previously prepared calibration curve.

[0111] (7) Amount of aluminum-based foreign matter 30 g of the polyester resin after solid-state polymerization 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 resin. 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 using an X-ray output of 50 kV and 70 mA, pentaerythritol as the analyzing crystal, a PC (proportional counter) as the detector, and Al-Kα line intensity at PHA (pulse height analyzer) 100-300. The aluminum content in the polyethylene terephthalate resin for the calibration curve was quantified using high-frequency inductively coupled plasma atomic emission spectrometry.

[0112] (8) Quantitation of cyclic trimers The polyester resin after solid-state polymerization or the hollow moldings formed by the method described below were frozen and crushed or fragmented, and 100 mg of the sample was precisely weighed. This was dissolved in 3 mL of a hexafluoroisopropanol / chloroform mixture (volume ratio = 2 / 3) and further diluted with 20 mL of chloroform. 10 mL of methanol was added to this to precipitate the polymer, which was then filtered. The filtrate was evaporated to dryness and made up to a constant volume with 10 mL of dimethylformamide. The amount of cyclic trimer in the polyester resin or hollow moldings was then quantified using the following high-performance liquid chromatography method. Equipment: L-7000 (Hitachi) Column: μ-Bondasphere C18 5μ 100 Å 3.9 mm × 15 cm (Waters) Solvent: Eluent A: 2% acetic acid / water (v / v) Eluent B: Acetonitrile Gradient B%: 10 → 100% (0 → 55 min) Flow rate: 0.8mL / min Temperature: 30℃ Detector: UV-259nm

[0113] The preparation of the aluminum-containing ethylene glycol solution and the phosphorus-containing ethylene glycol solution will be described below. (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.

[0114] (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 3, and the phosphorus-containing ethylene glycol solution b1 was used in all Examples and Comparative Examples other than Comparative Example 3.

[0115] [Example of batch polymerization method] Example 1 <Production of Polyester Resin> 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 12 ppm by mass and 32 ppm by mass, respectively, relative to the mass of the oligomer mixture. The amount of polyester resin 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 12 ppm by mass and 32 ppm by mass, respectively, relative to the mass of the polyester resin produced. Thereafter, the temperature of the system was raised to 280° C. in 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 with an IV of 0.60 dl / g. The obtained polyester resin was subjected to solid-state polymerization at 230° C. under reduced pressure for 7 hours using a batch-type solid-state polymerization apparatus to obtain a polyester resin having an IV of 0.75 dl / g.

[0116] <Production of hollow molded body> The polyester resin after solid-state polymerization was dried in a vacuum dryer to a moisture content of 100 ppm by mass or less, and a bottomed preform was molded using a Meiki Seisakusho 150C-DM injection molding machine and a preform mold (mold temperature: 5°C). The plasticization conditions for the M-150C-DM injection molding machine were a feed screw rotation speed of 70%, a screw rotation speed of 120 rpm, and a back pressure of 0.5 MPa. The cylinder temperatures were set to 45°C and 250°C from directly below the hopper, and 290°C from the nozzle onward. The injection pressure and dwell pressure were adjusted so that the molded product weight was 28.4 ± 0.2 g. The mouth of the preform was then heat-crystallized using an NC-01 mouth crystallizer manufactured by Frontier Corp. Furthermore, using a Sidel SBO Lab No. 1045 Type 1 Lab blow molding machine, the preform was biaxially stretch-blow molded into a mold set at 160°C at a pressure of 36 bar, at 750 bph, at a stretch ratio of 2.5 times in the longitudinal direction and 3.8 times in the circumferential direction, in a 30-second molding cycle, to obtain a hollow molded article.

[0117] (Examples 2 to 5, Comparative Examples 1 and 2) A polyester resin was obtained in the same manner as in Example 1, except that the aluminum-containing ethylene glycol solution a1 and the phosphorus-containing ethylene glycol solution b1 were added to the resulting polyester resin in amounts corresponding to the catalyst element addition amounts shown in Table 1. A hollow molded body was also obtained in the same manner as in Example 1.

[0118] (Comparative Example 3) A polyester resin was obtained in the same manner as in Example 1, except that the solution b1' was used as the phosphorus-containing ethylene glycol solution instead of the solution b1. A blown molded article was also obtained in the same manner as in Example 1.

[0119] The physical properties of the polyester resins obtained in Examples 1 to 5 and Comparative Examples 1 to 3 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.

[0120] [Table 1]

[0121] The polyester resins of Examples 1 to 5 have a short polymerization time despite the small amounts of aluminum and phosphorus added, and the polyester resins after solid-state polymerization have low amounts of aluminum-based foreign matter and CT, resulting in high quality. Furthermore, because the amount of catalyst added is small, catalyst costs can be reduced. Furthermore, because the blown molded body is produced using a polyester resin with a low CT amount, the CT amount of the blown molded body is also low. Comparative Example 1 is preferable in that the amount of phosphorus compound added is large, resulting in high catalyst costs, and the molar ratio of phosphorus added to aluminum is high, resulting in suppression of aluminum-based foreign matter, but is unfavorable in that the polymerization activity decreases and the catalyst costs increase. In Comparative Example 2, the residual molar ratio of phosphorus to aluminum was too low, which resulted in lower catalyst costs, but the amount of aluminum-based foreign matter in the polyester resin after solid-state polymerization increased, and the CT amount also increased, resulting in poor quality polyester resin. Furthermore, because the hollow molded body was produced using a polyester resin with a high CT amount, the CT amount of the hollow molded body was also high. In Comparative Example 3, 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 large compared to Examples 1 to 5, resulting in a low residual molar ratio of phosphorus to aluminum. This resulted in an increase in the amount of aluminum-based impurities in the polyester resin after solid-state polymerization, and a high CT content, resulting in poor quality of the polyester resin. Furthermore, because a polyester resin with a high CT content was used to produce the hollow molded body, the CT content of the hollow molded body was also high.

[0122] [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 the 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 the phosphorus-containing ethylene glycol solution b1 prepared by the above method were used as catalysts, and the aluminum and phosphorus contents were 12 ppm by mass and 32 ppm by mass, respectively, relative to the resulting oligomer, and the one-component solution was added. The amount of polyester resin 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 12 ppm by mass and 32 ppm by mass, respectively, relative to the polyester resin produced. 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 with an IV of 0.59 dL / g. The polyester resin was extruded into a strand, cooled in water, cut, and pelletized.

[0123] The resulting polyester resin chips were then transported to a continuous solid-state polymerization apparatus. They were crystallized at approximately 155°C under a nitrogen atmosphere, preheated to approximately 200°C under a nitrogen atmosphere, and then transferred to a continuous solid-state polymerization reactor for solid-state polymerization at approximately 207°C under a nitrogen atmosphere. Subsequently, the resulting material was subjected to a vibrating sieve and an air classification process to remove fine particles and film-like materials, yielding a polyester resin with an IV of 0.75 dL / g. A blown molded article was also obtained in the same manner as in Example 1.

[0124] (Examples 7 and 8, Comparative Examples 4 and 5) A polyester resin was obtained in the same manner as in Example 6, except that the aluminum-containing ethylene glycol solution a1 and the phosphorus-containing ethylene glycol solution b1 were added to the obtained oligomer in amounts corresponding to the catalyst elements shown in Table 2. A hollow molded body was also obtained in the same manner as in Example 1.

[0125] The physical properties of the polyester resins obtained in Examples 6 to 8 and Comparative Examples 4 and 5 are shown in Table 2.

[0126] [Table 2]

[0127] 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 5, with the hourly production volume of Comparative Example 4 as the standard (the hourly production volume of Comparative Example 4 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 of Examples 6 to 8 had a higher production volume ratio than Comparative Example 4, contained less aluminum and phosphorus, reduced catalyst costs, and improved polymerization activity. Furthermore, the amounts of aluminum-based foreign matter and CT in the polyester resin after solid-state polymerization were also low, resulting in high-quality polyester resins. Furthermore, because the blown molded bodies were produced using polyester resins with a low CT content, the CT content of the blown molded bodies was also low. In Comparative Example 5, the residual molar ratio of phosphorus to aluminum was too low, resulting in a large amount of aluminum-based foreign matter in the polyester resin after solid-state polymerization and a large CT amount, resulting in a polyester resin of poor quality. Furthermore, since a hollow molded body was produced using a polyester resin with a large CT amount, the CT amount of the hollow molded body was also large.

[0128] Using the results of Examples 1 to 5 and Comparative Examples 1 and 2 in Table 1, the relationship between the residual molar ratio of phosphorus element to aluminum element, the amount of aluminum-based foreign matter, and the polymerization time is shown in FIG. 1, and 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 FIG. 2.

[0129] These figures clearly show that the range of the present invention is critical, and that the amount of aluminum-based foreign matter and the polymerization time are trade-offs. [Industrial Applicability]

[0130] The polyester resin and blown molded article of the present invention produced using a polymerization catalyst comprising an aluminum compound and a phosphorus compound maintain color tone and thermal stability, while maintaining polymerization activity and suppressing the generation of aluminum-based foreign matter, and can also reduce catalyst costs. This makes it possible to provide clean, high-quality polyester resins, which will be a great contribution to industry.

Claims

1. A polyester resin containing an aluminum compound and a phosphorus compound, characterized in that the polyester resin satisfies the following (1) to (3): (1) The content of aluminum element in the polyester resin is 9 to 19 mass ppm. (2) The content of phosphorus element in the polyester resin is 22 to 40 mass ppm. (3) The molar ratio of phosphorus element to aluminum element in the polyester resin is 1.55 or more and 1.85 or less.

2. A polyester resin as described in claim 1, wherein the polyester resin contains a substance derived from a polymerization catalyst, and the polymerization catalyst contains only a polymerization catalyst consisting of the aluminum compound and the phosphorus compound.

3. 3. The polyester resin according to claim 1, wherein the content of aluminum elements corresponding to aluminum-based foreign matter in aluminum-based foreign matter in the polyester resin is 1650 mass ppm or less.

4. 4. The polyester resin according to claim 1, which has an intrinsic viscosity (IV) of 0.56 dl / g or more.

5. 5. The polyester resin according to claim 1, wherein the phosphorus compound has a phosphorus element and a phenol structure in the same molecule.

6. 6. The polyester resin according to claim 1, wherein the amount of cyclic trimer is 5,000 ppm or less.

7. A method for producing a polyester resin according to any one of claims 1 to 6, comprising the steps of: A first step of synthesizing a polyester or an oligomer thereof as a polycondensate as an intermediate; a second step of melt polymerizing the intermediate; a third step of solid-state polymerizing the melt-polymerized polyester; a solution A1 in which an aluminum compound is dissolved and a solution B1 in which a phosphorus compound is dissolved are simultaneously 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 (4) to (6): The solution A1 is a glycol solution, and the maximum absorption wavelength of the solution A1 is 562.0 to 572.0 nm; The solution B1 is a glycol solution, and the solution B1 has a maximum absorption wavelength of 460.0 to 463.0 nm. (4) The amount of aluminum element added to the polyester resin to be produced is 9 to 19 mass ppm. (5) The amount of phosphorus added to the polyester resin to be produced is 25 to 50 mass ppm. (6) The molar ratio of the amount of phosphorus element added in (5) to the amount of aluminum element added in (4) is 2.00 or more and 2.40 or less.

8. A method for producing a polyester resin as described in Claim 7, wherein the second step is carried out using only a polymerization catalyst consisting of the aluminum compound and the phosphorus compound as the polymerization catalyst.

9. 9. The method for producing a polyester resin according to claim 7, wherein the melt polymerization is carried out until the intrinsic viscosity (IV) reaches 0.56 to 0.65 dL / g, and then the solid-state polymerization is carried out until the intrinsic viscosity (IV) reaches 0.70 to 0.85 dL / g.

10. 8. The method for producing a polyester resin according to claim 7, wherein the glycol solution B1 is prepared by heat-treating a phosphorus compound in a glycol solution at 170 to 196° C. for 125 to 240 minutes.

11. The method for producing a polyester resin according to any one of claims 7 to 10, 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.

12. A hollow molded body formed from a polyester resin containing an aluminum compound and a phosphorus compound, the hollow molded body satisfying the following (7) to (9): (7) The aluminum element content in the hollow molded body is 9 to 19 mass ppm. (8) The content of phosphorus element in the hollow molded body is 22 to 40 mass ppm. (9) The molar ratio of phosphorus element to aluminum element in the hollow molded body is 1.55 or more and 1.85 or less.

13. A hollow molded body as described in Claim 12, wherein the polyester resin constituting the hollow molded body contains a substance derived from a polymerization catalyst, and the polymerization catalyst contains only a polymerization catalyst consisting of the aluminum compound and the phosphorus compound.

14. 14. The blow molded body according to claim 12 or 13, wherein the content of aluminum element corresponding to aluminum-based foreign matter in aluminum-based foreign matter contained in the polyester resin constituting the blow molded body is 1650 mass ppm or less.

15. The blown molded article according to any one of claims 12 to 14, wherein the phosphorus compound has a phosphorus element and a phenol structure in the same molecule.

16. The blow molded article according to any one of claims 12 to 15, wherein the amount of cyclic trimer is 6000 ppm or less.

17. A method for producing the hollow molded article according to any one of claims 12 to 16, comprising molding the polyester resin according to any one of claims 1 to 6 to produce the hollow molded article.

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