Polyester resin and method for producing polyester resin

Abstract

The present invention provides a high-quality polyester resin produced using a polymerization catalyst comprising an aluminum compound and a phosphorus compound. The present invention can attain a reduction in catalyst cost. The catalyst has high polymerization activity and leaves less foreign substances in the resin. The polyester resin contains the aluminum compound and the phosphorus compound which were used as the catalyst, and has an aluminum atom content of 9-20 ppm and a phosphorus atom content of 13-31 ppm, the molar ratio of the phosphorus atoms to the aluminum atoms being 1.32-1.80.

Description

Technical Field

[0001] The present invention relates to a polyester resin and a method for producing the same. More specifically, the present invention relates to a polyester resin and a method for producing the same, which use an aluminum compound and a phosphorus compound as main catalyst components, achieve both suppression of catalyst-derived foreign substances and polymerization activity, and further reduce the catalyst cost.

Background Art

[0002] Polyesters typified by polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polyethylene naphthalate (PEN), etc. are excellent in mechanical properties and chemical properties. Depending on the properties of each polyester, they are widely used in various fields, such as fibers for clothing and industrial materials, various films and sheets for packaging and industry, and molded articles such as bottles and engineering plastics.

[0003] For example, in the case of polyethylene terephthalate (PET), a polyester mainly composed of an aromatic dicarboxylic acid and an alkylene glycol, bis(2-hydroxyethyl) terephthalate is produced by esterification or transesterification of terephthalic acid or dimethyl terephthalate with ethylene glycol, and then industrially produced by a polycondensation method such as polycondensing this under high temperature and vacuum using a catalyst.

[0004] Conventionally, as a polyester polymerization catalyst used during the polymerization of such polyester resins, antimony compounds or germanium compounds have been widely used. Antimony trioxide is a catalyst that is inexpensive and has excellent catalytic activity. However, when it is used with this as the main component, that is, when used in an amount such that a practical polymerization rate is exhibited, metallic antimony precipitates during polymerization, resulting in blackening and foreign matter in the polyester resin, which also causes surface defects in the film. Further, when used as a raw material for hollow molded articles and the like, it is difficult to obtain a hollow molded article with excellent transparency. For these reasons, a polyester resin that does not contain any antimony compounds or does not contain an antimony compound as the main component of the catalyst is desired.

[0005] As a catalyst that has excellent catalytic activity other than antimony compounds and provides a polyester resin that does not have the above problems, germanium compounds have already been put into practical use. However, this catalyst has problems such as being very expensive, and because it easily distills out of the reaction system during polymerization, the catalyst concentration in the reaction system changes and it becomes difficult to control the polymerization. There are problems with using it as the main component of the catalyst.

[0006] Studies have also been conducted on polymerization catalysts to replace antimony-based or germanium-based catalysts. Titanium compounds typified by tetraalkoxytitanate have already been proposed. However, polyester resins produced using these have problems such as being easily thermally degraded during melt molding and the polyester resin being significantly colored.

[0007] For the reasons described above, a polymerization catalyst is desired that has a metal component other than antimony-based, germanium-based, and titanium-based as the main metal component of the catalyst, has excellent catalytic activity, excellent color tone and thermal stability, and provides a polyester resin with excellent transparency of the molded article.

[0008] As a novel polymerization catalyst, a catalyst system composed of an aluminum compound and a phosphorus compound has been disclosed and attracted attention (see, for example, Patent Documents 1 and 2). By using the above polymerization catalyst, a polyester resin with good color tone, transparency, and thermal stability can be obtained. However, in this method, since the amount of catalyst added is large and the cost of the phosphorus compound used is also high, there is a problem that the catalyst cost required for polymerization becomes high. In addition, in order to obtain a high-quality polyester resin while maintaining high polymerization activity, it is necessary to increase the addition amounts of the aluminum compound and the phosphorus compound, which are the catalysts, and as a result, there has been a problem that the catalyst cost becomes high.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0010] The present invention has been made to solve such problems of the prior art, and an object thereof is to provide a polyester resin and a method for producing a polyester resin that can reduce the catalyst cost, have high polymerization activity, and have few foreign substances in the resin, and are produced using a polymerization catalyst composed of an aluminum compound and a phosphorus compound.

Means for Solving the Problems

[0011] As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by reducing the amount of aluminum atoms contained in the polyester resin and setting the molar ratio of phosphorus atoms to aluminum atoms within an appropriate range, and have reached the present invention. In polymerization catalysts such as antimony compounds and germanium compounds used in polyester polymerization, the polymerization activity generally is proportional to the catalyst addition amount. However, in a polymerization catalyst composed of an aluminum compound and a phosphorus compound, since the complex formation reaction between the aluminum compound and the phosphorus compound affects the polymerization activity, the relationship between the polymerization activity and the catalyst addition amount cannot be simplified.

[0012] Therefore, the inventors of the present invention analyzed the controlling factors of the catalyst activity for a polymerization catalyst composed of an aluminum compound and a phosphorus compound. As a result, by reducing the amount of aluminum atoms in the polyester resin, setting the molar ratio of phosphorus atoms to aluminum atoms within an appropriate range, and further setting the acidity or basicity of the aluminum compound solution, phosphorus compound solution, and their mixed solution added as a catalyst within a preferable range, it was found that the amount of aluminum-based foreign substances can be suppressed while suppressing an increase in the catalyst cost and improving the polymerization activity, and the present invention was completed.

[0013] That is, the present invention is composed of the following configurations. [1] A polyester resin containing an aluminum compound and a phosphorus compound used as a catalyst, characterized in that the following formulas (1) to (3) are satisfied. (1) 9 ≦ Al ≦ 20 (2) 13 ≦ P ≦ 31 (3) 1.32 ≦ P / Al ≦ 1.80 [In the above formulas (1) to (3), Al represents the amount (ppm) based on the mass of aluminum atoms contained in the polyester resin, P represents the amount (ppm) based on the mass of phosphorus atoms contained in the polyester resin, and P / Al represents the molar ratio of phosphorus atoms to aluminum atoms in the polyester resin.]

[0014] [2] The polyester resin according to [1], characterized in that the content of aluminum-based foreign substances is 3000 ppm or less with respect to the mass of the polyester resin.

[0015] [3] The polyester resin according to [1] or [2], characterized in that the intrinsic viscosity (IV) is 0.56 dl / g or more.

[0016] [4] The polyester resin according to any one of [1] to [3], characterized in that the phosphorus compound is a dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate.

[0017] [5] In a method for producing a polyester resin by a batch polymerization method, an aluminum compound and a phosphorus compound are used as catalysts, the phosphorus compound is a dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, and after the esterification reaction is completed, an ethylene glycol solution of the aluminum compound and an ethylene glycol solution of the phosphorus compound are added in amounts satisfying the following formulas (4) to (6). A method for producing a polyester resin, characterized by the above. (4) 9 ≦ Al ≦ 20 (5) 20 ≦ P ≦ 40 (6) 1.50 ≦ P / Al ≦ 2.50 [In the above formulas (4) to (6), Al represents the amount (ppm) on a mass basis of aluminum atoms with respect to the polyester to be produced, P represents the amount (ppm) on a mass basis of phosphorus atoms with respect to the polyester to be produced, and P / Al represents the molar ratio of the amount of phosphorus atoms in formula (5) to the amount of aluminum atoms in formula (4).]

[0018] [6] In a method for producing a polyester resin by a continuous polymerization method, an aluminum compound and a phosphorus compound are used as catalysts, the phosphorus compound is a dialkyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, and an ethylene glycol solution of the aluminum compound and an ethylene glycol solution of the phosphorus compound are added in amounts satisfying the following formulas (4) to (6) at the outlet of the final esterification reaction tank or in the transfer line between the final esterification reaction tank and the initial polymerization reaction tank. A method for producing a polyester resin, characterized by the above. (4) 9 ≦ Al ≦ 20 (5) 20 ≦ P ≦ 40 (6) 1.50 ≦ P / Al ≦ 2.50 [In the above formulas (4) to (6), Al represents the amount (ppm) based on the mass of aluminum atoms with respect to the polyester to be produced, P represents the amount (ppm) based on the mass of phosphorus atoms with respect to the polyester to be produced, and P / Al represents the molar ratio of the amount of phosphorus atoms in formula (5) to the amount of aluminum atoms in formula (4).]

[0019] [7] A method for producing a polyester resin according to any one of [5] to [6], characterized in that a solution having a maximum absorption wavelength measured by the following color reaction P in the range of 458.0 to 465.0 nm is used as the ethylene glycol solution of the phosphorus compound. (Here, the maximum absorption wavelength measured by the color reaction P is obtained by adding 4 mL of ethylene glycol and 0.3 mL of a 1 mmol / L aqueous solution of Bismarck Brown, which is a basic dye, to a sample bottle, then adding 0.1 mL of the ethylene glycol solution of the phosphorus compound, shaking for 10 seconds until the solution becomes homogeneous, then allowing to stand at room temperature for 10 minutes, and then measuring the absorption spectrum using an ultraviolet-visible spectrophotometer.)

[0020] [8] A method for producing a polyester resin according to any one of [5] to [7], characterized in that when preparing the ethylene glycol solution of the phosphorus compound, heat treatment is performed at 175 to 196 °C for 30 to 240 minutes.

[0021] [9] A method for producing a polyester resin according to any one of [5] to [8], characterized in that a solution having a maximum absorption wavelength measured by the following color reaction A in the range of 562.0 to 572.0 nm is used as the ethylene glycol solution of the aluminum compound. (Here, the maximum absorption wavelength measured by the color reaction A is obtained by adding 4 mL of ethylene glycol and 0.3 mL of a 1 mmol / L aqueous solution of Mordant Blue 13, which is an acidic dye, to a sample bottle, then adding 0.1 mL of the ethylene glycol solution of the aluminum compound, shaking for 10 seconds until the solution becomes homogeneous, then allowing to stand at room temperature for 10 minutes, and then measuring the absorption spectrum using an ultraviolet-visible spectrophotometer.)

[0022]

[10] As the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound, a solution having a maximum absorption wavelength measured by the following color reaction AP of the mixed solution obtained by mixing the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound in the amount ratio added to the polyester resin production process is 559.5 to 561.5 nm is used. A method for producing a polyester resin according to any one of [5] to [9]. (Here, the maximum absorption wavelength measured by the color reaction AP is obtained by adding 4 mL of ethylene glycol and 0.3 mL of 1 mmol / L Mordant Blue 13 aqueous solution, which is an acidic dye, to a sample bottle, and then adding 0.1 mL of a mixed solution of the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound, shaking for 10 seconds until the solution becomes uniform, and then standing at room temperature for 10 minutes. After that, the absorption spectrum is measured using an ultraviolet-visible spectrophotometer.)

Effect of the Invention

[0023] The polyester resin of the present invention can improve the productivity of the polyester resin while keeping the catalyst cost low, which was a problem of the polymerization catalyst composed of the aluminum compound and the phosphorus compound, and can reduce the foreign matters derived from the catalyst contained in the polyester resin.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Best Mode for Carrying Out the Invention

[0025] The present invention will be described in detail below. In the present invention, the polyester resin refers to a polyester as a chemical substance containing a catalyst component (including components in which the catalyst described later has changed in structure, foreign components derived from the catalyst, etc.). In this specification, "polyester" and "polyester resin" are described separately as much as possible, but for convenience, they may be described without distinction.

[0026] The polyester in the present invention refers to a polyester composed of one or more selected from polyvalent carboxylic acids containing dicarboxylic acids and their ester-forming derivatives and one or more selected from polyhydric alcohols containing glycols, or a polyester composed of hydroxycarboxylic acids and their ester-forming derivatives, or a polyester composed of cyclic esters.

[0027] Preferred polyesters are polyesters in which the main polyvalent carboxylic acid component is terephthalic acid or its ester-forming derivative, or naphthalenedicarboxylic acid or its ester-forming derivative, and the main polyhydric alcohol component is alkylene glycol.

[0028] The polyester in which the main polyvalent carboxylic acid component is terephthalic acid or its ester-forming derivative or naphthalenedicarboxylic acid or its ester-forming derivative is preferably a polyester containing 70 mol% or more in total of terephthalic acid or its ester-forming derivative and naphthalenedicarboxylic acid or its ester-forming derivative with respect to all polyvalent carboxylic acid components, more preferably a polyester containing 80 mol% or more, and still more preferably a polyester containing 90 mol% or more.

[0029] The polyester in which the main polyhydric alcohol component is alkylene glycol is preferably a polyester containing 70 mol% or more of alkylene glycol in total with respect to all polyhydric alcohol components, more preferably a polyester containing 80 mol% or more, and even more preferably a polyester containing 90 mol% or more.

[0030] Examples of the dicarboxylic acid 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, dimer acid, or ester-forming derivatives thereof; unsaturated aliphatic dicarboxylic acids such as fumaric acid, maleic acid, itaconic acid, or ester-forming derivatives thereof; aromatic dicarboxylic acids such as 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, or ester-forming derivatives thereof.

[0031] Among these dicarboxylic acids, terephthalic acid, naphthalenedicarboxylic acid, or ester-forming derivatives thereof are preferred.

[0032] Examples of the 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.

[0033] Particularly preferred are terephthalic acid, 2,6-naphthalenedicarboxylic acid or their ester-forming derivatives. If necessary, other dicarboxylic acids may be used as constituent components.

[0034] Examples of polycarboxylic acids other than these dicarboxylic acids include ethanetricarboxylic acid, propanetricarboxylic acid, butanetetracarboxylic acid, pyromellitic acid, trimellitic acid, trimesic acid, 3,4,3’,4’-biphenyltetracarboxylic acid, and their ester-forming derivatives.

[0035] Examples of glycols include alkylene glycols such as 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, 1,12 - dodecanediol; aliphatic glycols exemplified by polyethylene glycol, polytrimethylene glycol, polytetramethylene glycol; aromatic glycols such as 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; and glycols obtained by adding ethylene oxide to these glycols.

[0036] Among these glycols, alkylene glycols are preferred, and more preferably ethylene glycol, 1,3 - propylene glycol, 1,4 - butylene glycol, 1,4 - cyclohexanedimethanol. Also, the alkylene glycol may contain a substituent or an alicyclic structure in the molecular chain, and two or more kinds may be used simultaneously.

[0037] Examples of polyhydric alcohols other than these glycols include trimethylolmethane, trimethylolethane, trimethylolpropane, pentaerythritol, glycerol, hexanetriol, etc.

[0038] Examples of the hydroxycarboxylic acid 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, or ester-forming derivatives thereof.

[0039] Examples of the cyclic ester include ε-caprolactone, β-propiolactone, β-methyl-β-propiolactone, δ-valerolactone, glycolide, lactide, and the like.

[0040] Examples of the ester-forming derivatives of the polyvalent carboxylic acid or hydroxycarboxylic acid include their alkyl esters, acid chlorides, acid anhydrides, and the like.

[0041] Preferred examples of the polyester used in the present invention include polyethylene terephthalate, polybutylene terephthalate, polypropylene terephthalate, poly(1,4-cyclohexanedimethylene terephthalate), polyethylene naphthalate, polybutylene naphthalate, polypropylene naphthalate, and copolymers thereof, and particularly preferred are polyethylene terephthalate and its copolymers.

[0042] The polyester resin of the present invention needs to contain, as a catalyst, an aluminum compound and a phosphorus compound in amounts satisfying the following formulas (1) to (3). (1) 9 ≦ Al ≦ 20 (2) 13 ≦ P ≦ 31 (3) 1.32 ≦ P / Al ≦ 1.80 [In the above formulas (1) to (3), Al represents the amount (ppm) based on the mass of aluminum atoms contained in the polyester resin, P represents the amount (ppm) based on the mass of phosphorus atoms contained in the polyester resin, and P / Al represents the molar ratio of phosphorus atoms to aluminum atoms in the polyester resin.] In the present invention, "ppm" represents a value based on mass unless otherwise specified.

[0043] In the present invention, the content of aluminum atoms in the polyester resin needs to be 9 to 20 ppm, preferably 9 to 19 ppm, more preferably 10 to 17 ppm, and still more preferably 12 to 17 ppm. When the content of aluminum atoms is less than the above range, the catalytic activity may not be fully exerted. On the other hand, when the content of aluminum atoms exceeds the above range, the amount of aluminum-based foreign matter described later may increase, and in addition, the cost of the catalyst increases, which is not preferable.

[0044] Also, in the present invention, the content of phosphorus atoms in the polyester resin needs to be 13 to 31 ppm, preferably 15 to 29 ppm, and more preferably 16 to 28 ppm. When the content of phosphorus atoms is less than the above range, the catalytic activity may not be fully exerted, or the amount of aluminum-based foreign matter described later may increase. On the other hand, when the content of phosphorus atoms exceeds the above range, the polymerization activity may be conversely decreased, and in addition, the cost of the catalyst increases, which is not preferable.

[0045] Furthermore, in the present invention, the molar ratio of phosphorus atoms to aluminum atoms contained in the polyester resin, that is, remaining in the polyester resin (hereinafter referred to as the "remaining molar ratio of phosphorus atoms to aluminum atoms" to distinguish it from the "added molar ratio of phosphorus atoms to aluminum atoms" described later) is also important. Specifically, the remaining molar ratio of phosphorus atoms to aluminum atoms (P / Al ratio) in the polyester resin needs to be 1.32 to 1.80, preferably 1.38 to 1.68. As described above, the aluminum atoms and phosphorus atoms in the polyester resin are respectively derived from the aluminum compound and the phosphorus compound used as the polymerization catalyst of the polyester resin. By using these aluminum compounds and phosphorus compounds in a specific ratio, a complex having catalytic activity is functionally formed in the polymerization system, and sufficient polymerization activity can be exerted. When the remaining molar ratio of phosphorus atoms to aluminum atoms in the polyester resin is less than the above range, problems such as a decrease in thermal stability and thermo-oxidative stability may occur, or the amount of aluminum-based foreign matter described later may increase. On the other hand, when the remaining molar ratio of phosphorus atoms to aluminum atoms in the polyester resin exceeds the above range, it is not preferable because the cost of the catalyst increases.

[0046] As the aluminum compound in the present invention, known aluminum compounds can be used without limitation.

[0047] Specific examples of the aluminum compound include carboxylates such as aluminum formate, aluminum acetate, basic aluminum acetate, aluminum propionate, and aluminum oxalate; inorganic acid salts such as aluminum chloride, aluminum hydroxide, and aluminum hydroxychloride; aluminum alkoxides such as aluminum methoxide, aluminum ethoxide, aluminum isopropoxide, aluminum n-butoxide, and aluminum t-butoxide; aluminum chelate compounds such as aluminum acetylacetonate and aluminum acetylacetate; organoaluminum compounds such as trimethylaluminum and triethylaluminum and their partial hydrolyzates; and aluminum oxide. Among these, carboxylates, inorganic acid salts, and chelate compounds are preferable, and among these, aluminum acetate, basic aluminum acetate, aluminum chloride, aluminum hydroxide, aluminum hydroxychloride, and aluminum acetylacetonate are more preferable, and aluminum acetate and basic aluminum acetate are most preferable.

[0048] As the phosphorus compound in the present invention, it is preferably a dialkyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid. The compound is a compound represented by Chemical Formula (1).

[0049]

Chemical formula

[0050] (In Chemical Formula (1), R 1 , R 2 each represents hydrogen or an alkyl group having 1 to 4 carbon atoms.)

[0051] The alkyl group in Chemical Formula (1) preferably has 1 to 4 carbon atoms. In particular, the ethyl ester form having 2 carbon atoms is preferable because Irganox 1222 (manufactured by BASF) is commercially available and easily obtainable. This compound is represented by Chemical Formula (1-a).

[0052]

Chemical Formula

[0053] In the present invention, in addition to the above-mentioned aluminum compound and phosphorus compound, other polycondensation catalysts such as antimony compounds, germanium compounds, and titanium compounds may be used in combination within a range that does not cause problems in the properties, processability, color tone, etc. of the polyester resin of the present invention. In that case, for the obtained polyester resin, the content of the antimony compound as antimony atoms is preferably 30 ppm or less, the content of the germanium compound as germanium atoms is preferably 10 ppm or less, and the content of the titanium compound as titanium atoms is preferably 3 ppm or less. However, for the purpose of the present invention, it is preferably not to use these other polycondensation catalysts such as antimony compounds, germanium compounds, and titanium compounds as much as possible.

[0054] The polyester resin of the present invention preferably has an aluminum-based foreign matter content of 3000 ppm or less, more preferably 2800 ppm or less, still more preferably 2500 ppm or less, and particularly preferably 2300 ppm or less, based on the mass of the polyester resin. The aluminum-based foreign matter is caused by the aluminum compound used as the polymerization catalyst and is a foreign matter insoluble in the polyester resin. If the content of the aluminum-based foreign matter exceeds the above, fine foreign matter insoluble in the polyester resin will cause deterioration in the quality of fibers, films, molded articles, etc., which is not preferable. It also leads to the problem of increased filter clogging during polyester filtration in the polycondensation process and the molding process. The preferable lower limit of the aluminum-based foreign matter is 0 ppm, but about 300 ppm can be achieved in the present invention. The method for measuring the amount of aluminum-based foreign matter was carried out according to the evaluation method (4) in the examples described later. As can be seen from this measurement method, this index relatively evaluates the amount of aluminum-based foreign matter and does not indicate the absolute value of the amount of foreign matter contained in the polyester resin.

[0055] The intrinsic viscosity (IV) of the polyester resin of the present invention is preferably 0.56 dl / g or more, more preferably 0.56 to 1.00 dl / g, and still more preferably 0.60 to 0.85 dl / g. If the intrinsic viscosity of the polyester resin is less than the above, the mechanical strength and impact resistance of the molded article may be insufficient. On the other hand, if the intrinsic viscosity of the polyester resin exceeds the above range, the economy will decrease, which is not preferable.

[0056] The polyester resin of the present invention preferably has a back pressure increase coefficient (k) of 0.40 or less, more preferably 0.30 or less. When the back pressure increase coefficient (k) exceeds the above, the frequency of filter clogging during melt molding of the polyester resin into fibers, films, molded articles, etc. increases, and the productivity decreases due to frequent filter replacement, resulting in increased costs, which is not preferable. The preferable lower limit of the back pressure increase coefficient (k) is 0, but it is about 0.1 due to technical constraints. The measurement method of the back pressure increase coefficient (k) was carried out according to the evaluation method (8) in the examples described later.

[0057] Next, the method for producing the polyester resin of the present invention will be described. The production method of the polyester resin is not particularly limited, and an oligomer of a polyvalent carboxylic acid containing terephthalic acid or the like and a polyhydric alcohol can be obtained by a direct esterification method of a polyvalent carboxylic acid and a polyhydric alcohol, or a transesterification method of an alkyl ester of terephthalic acid or the like and a polyhydric alcohol. Thereafter, a polyester resin can be obtained by melt polycondensation under normal pressure or reduced pressure. At this time, an esterification catalyst or the above polycondensation catalyst can be used as necessary. The polymerization method may be a batch polymerization method or a continuous polymerization method. Also, the polymerization apparatus may be batch type or continuous type.

[0058] The production of the polyester resin according to the present invention can be carried out by a method having a conventionally known process except for using a polyester polymerization catalyst composed of an aluminum compound and a phosphorus compound and paying attention to the following method of adding the polymerization catalyst. For example, when producing PET, a direct esterification method in which terephthalic acid and ethylene glycol, and optionally other copolymerization components are directly reacted, water is distilled off and esterified, and then polycondensation is carried out under reduced pressure, or dimethyl terephthalate and ethylene glycol, and optionally other copolymerization components are reacted to distill off methyl alcohol and transesterified, and then polycondensation is carried out under reduced pressure. Further, if necessary, solid-phase polymerization may be carried out to increase the intrinsic viscosity.

[0059] In any of these methods, the esterification reaction or the transesterification reaction may be carried out in one step or may be carried out in multiple steps. The melt polycondensation reaction may also be carried out in one step or may be carried out in multiple steps. The solid-phase polymerization reaction can be carried out in a continuous apparatus similar to the melt polycondensation reaction.

[0060] When using an aluminum compound and a phosphorus compound as catalysts, it is preferable to add them in a slurry or solution state, more preferably solubilized in a solvent such as water or glycol, even more preferably solubilized in water and / or ethylene glycol, and most preferably using a solubilized product in ethylene glycol.

[0061] In the present invention, after completion of the esterification reaction or transesterification reaction, it is preferable to add an ethylene glycol solution of an aluminum compound and an ethylene glycol solution of a phosphorus compound so as to fall within the range of the preferable content (remaining amount) in the above-mentioned polyester resin. If added before completion of the esterification reaction or transesterification reaction, the amount of aluminum-based foreign substances may increase.

[0062] By adding an ethylene glycol solution of an aluminum compound and an ethylene glycol solution of a phosphorus compound so as to satisfy the range of the preferable content (remaining amount) in the above-mentioned polyester resin, a complex having catalytic activity is functionally formed in the polymerization system, and sufficient polymerization activity can be exhibited. Also, the generation of aluminum-based foreign substances can be suppressed.

[0063] Note that the aluminum atoms in the aluminum compound that function as a catalyst, even when placed in a reduced-pressure environment during the polymerization of the polyester resin, almost 100% of the amount used initially added to the system as a catalyst remains in the polyester resin produced by polymerization. Therefore, if the aluminum compound is added within the above range, the remaining amount in the polyester resin will be the required aluminum remaining amount.

[0064] In addition, when the phosphorus compound that functions as a catalyst together with the aluminum compound is placed in a reduced-pressure environment during the polymerization of the polyester resin, a part (about 10 to 40%) of the amount initially added to the system as a catalyst is removed outside the system. This removal ratio varies depending on the addition molar ratio of the aluminum compound and the phosphorus compound, the basicity or acidity of the aluminum compound solution and the phosphorus compound solution to be added, the addition method of the aluminum compound solution and the phosphorus compound solution (whether to add them in one liquid or separately), and the like. Therefore, it is preferable to appropriately set so as to fall within the preferable range in the above-mentioned polyester resin.

[0065] The production method in the case of using a dialkyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid as the phosphorus compound will be described in detail. Whether it is a batch polymerization method or a continuous polymerization method, an aluminum compound and a phosphorus compound are used as catalysts, and after the esterification reaction is completed, it is preferable to add an ethylene glycol solution of the aluminum compound and an ethylene glycol solution of the phosphorus compound in amounts that satisfy the following formulas (4) to (6). (4) 9 ≦ Al ≦ 20 (5) 20 ≦ P ≦ 40 (6) 1.50 ≦ P / Al ≦ 2.50 [In the above formulas (4) to (6), Al represents the amount (ppm) on a mass basis of aluminum atoms with respect to the polyester to be produced, P represents the amount (ppm) on a mass basis of phosphorus atoms with respect to the polyester to be produced, and P / Al represents the molar ratio of the amount of phosphorus atoms in formula (5) to the amount of aluminum atoms added in formula (4).] (6) The P / Al in formula (6) may also be referred to as the addition molar ratio of phosphorus atoms to aluminum atoms. The addition amount of aluminum atoms is more preferably 9 to 19 ppm. The addition amount of phosphorus atoms is preferably 20 to 38 ppm. The addition molar ratio of phosphorus atoms to aluminum atoms is more preferably 1.50 to 2.30. Note that the amount (mass) of the polyester to be produced can be calculated from the amount (mass) of the polyvalent carboxylic acid containing terephthalic acid or the like used as a raw material.

[0066] The maximum absorption wavelengths of the ethylene glycol solution of an aluminum compound and the ethylene glycol solution of a phosphorus compound will be described below. By controlling the maximum absorption wavelengths of the ethylene glycol solution of an aluminum compound and the ethylene glycol solution of a phosphorus compound within a specific range, the polymerization activity can be stabilized, and a polyester resin with stable quality can be obtained. By controlling the maximum absorption wavelengths of the ethylene glycol solution of an aluminum compound and the ethylene glycol solution of a phosphorus compound within a specific range, the Lewis acid / base characteristics of the ethylene glycol solution of an aluminum compound and the ethylene glycol solution of a phosphorus compound can be controlled within a specific range, and the Lewis acid / base characteristics affect the complex formation reaction between the aluminum compound and the phosphorus compound, and it is presumed that the complex formation reaction affects the polymerization activity.

[0067] The color reaction A in the present invention will be described. The ethylene glycol solution of the aluminum compound used in the present invention preferably has a maximum absorption wavelength of 562.0 to 572.0 nm as measured after mixing with a 1 mmol / L aqueous solution of Mordant Blue 13, which is an acid dye. More preferably, it is 567.0 to 572.0 nm.

[0068] In order for the aluminum compound to functionally form a complex having catalytic activity with the phosphorus compound and exhibit polymerization activity, it is important to set the basicity of the aluminum compound contained in the ethylene glycol solution within a specific range.

[0069] The above maximum absorption wavelength is affected by the type and addition amount of the aluminum compound used, or the temperature, pressure, time, etc. during the preparation of the ethylene glycol solution. For example, it is a preferred embodiment to use an aluminum compound having an aluminum content within a specific range, or to perform treatment under reduced pressure or in a vacuum when converting an aqueous solution into an ethylene glycol solution in the preparation of the ethylene glycol solution of the aluminum compound.

[0070] When the maximum absorption wavelength is less than the above range, the basicity of the aluminum compound in the solution is low, and the complex with the phosphorus compound is not sufficiently formed, so the polymerization activity may decrease or the amount of aluminum-based foreign matter may increase. On the other hand, it is technically difficult for the maximum absorption wavelength to exceed the above range. The method for measuring the maximum absorption wavelength (color reaction A) of the aluminum compound ethylene glycol solution was carried out according to the evaluation method (6) in the examples described later.

[0071] The color reaction P in the present invention will be described. The ethylene glycol solution of the phosphorus compound used in the present invention preferably has a maximum absorption wavelength of 458.0 to 465.0 nm when measured after mixing with a 1 mmol / L aqueous solution of Bismarck Brown, which is a basic dye. More preferably, it is 460.0 to 463.0 nm, and even more preferably 461.0 to 462.0 nm.

[0072] In order for the phosphorus compound to functionally form a complex having catalytic activity with the aluminum compound and exhibit polymerization activity, it is important to set the acidity of the phosphorus compound contained in the ethylene glycol solution within a specific range.

[0073] The above maximum absorption wavelength is affected by the type and addition amount of the phosphorus compound used, or the temperature, pressure, time, etc. during the preparation of the ethylene glycol solution. When the maximum absorption wavelength exceeds the above range, the acidity of the phosphorus compound is low, and the complex with the aluminum compound is not sufficiently formed. Therefore, it is not preferable because the aluminum-based foreign matter increases due to the distillation of the phosphorus compound outside the polymerization system. Conversely, when the maximum absorption wavelength is less than the above range, the acidity of the phosphorus compound is high, and the bond with the aluminum compound becomes strong, so there is a risk of a significant decrease in polymerization activity. The method for measuring the maximum absorption wavelength (color reaction P) of the phosphorus compound ethylene glycol solution was carried out according to the evaluation method (5) in the examples described later.

[0074] In addition, it is preferable to use an ethylene glycol solution of the phosphorus compound used in the present invention that has been heat-treated in ethylene glycol in advance. The heat treatment in ethylene glycol is preferably carried out after dissolving the phosphorus compound, but it does not have to be completely dissolved.

[0075] The conditions for the above heat treatment are preferably such that the heat treatment temperature is 175 to 196 °C, more preferably 175 to 185 °C, still more preferably 175 to 180 °C. The heat treatment time is preferably 30 to 240 minutes, more preferably 60 to 210 minutes, still more preferably 125 to 210 minutes, and particularly preferably 140 to 210 minutes.

[0076] The concentration of the phosphorus compound during the above heat treatment is preferably 3 to 10% by mass.

[0077] By the above heat treatment, the acidity of the phosphorus compound contained in the ethylene glycol solution can be made constant, the polymerization activity by using it in combination with an aluminum compound can be improved, and the generation amount of aluminum-based foreign matters caused by the polymerization catalyst can be reduced.

[0078] In the above heat treatment, a part of the dialkyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, which is the phosphorus compound represented by Chemical Formula (1) used in the present invention, undergoes a structural change. For example, it changes to the elimination of the t-butyl group, the hydrolysis of the ethyl ester group, and the hydroxyethyl ester structure (ester exchange structure with ethylene glycol), etc. (Note that the elimination of the t-butyl group occurs remarkably under the high temperature in the polymerization step). Therefore, in the present invention, when the phosphorus compound is diethyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid, in addition to the phosphorus compound represented by Chemical Formula (1-a), phosphorus compounds with structural changes such as those represented by Chemical Formulas (1-b) to (1-j) are also included. The amount of each component of the phosphorus compound species in the ethylene glycol solution of the above phosphorus compound can be quantified by the P-NMR spectrum measurement method of the solution.

[0079] [Chemical formula]

[0080] Therefore, as the phosphorus compound in the present invention, in addition to diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate, modified forms of diethyl 3,5-di-tert-butyl-4-hydroxybenzylphosphonate represented by the above chemical formulas (1-b) to (1-j) are also included.

[0081] The color reaction AP in the present invention will be described. The mixed solution obtained by mixing the aluminum compound ethylene glycol solution and the phosphorus compound ethylene glycol solution used in the present invention in the amount ratio added to the production process of the polyester resin preferably has a maximum absorption wavelength of 559.5 to 561.5 nm when measured after mixing with a 1 mmol / L aqueous solution of mordant blue 13, which is an acid dye. More preferably, it is 559.5 to 561.0 nm, still more preferably 559.5 to 560.8 nm, and particularly preferably 559.7 to 560.6 nm.

[0082] By setting the maximum absorption wavelength of the mixed solution within the above range, the complex formation reaction between the aluminum compound and the phosphorus compound can be preferably maintained in a state that achieves both polymerization activity and suppression of aluminum-based foreign matters, which is preferable.

[0083] When the maximum absorption wavelength exceeds the above range, the basicity of the mixed solution of the aluminum compound ethylene glycol solution and the phosphorus compound ethylene glycol solution is high, and the polymerization system of the polyester resin is acidic. Therefore, when the mixed solution of the aluminum compound ethylene glycol solution and the phosphorus compound ethylene glycol solution is added to the polymerization system, the aluminum compound neutralizes with the carboxyl group end of the polyester resin and forms foreign substances, which may increase the amount of aluminum-based foreign substances. Conversely, when the maximum absorption wavelength is less than the above range, the basicity of the mixed solution of the aluminum compound ethylene glycol solution and the ethylene glycol solution of the phosphorus compound becomes too low, the coordination between the aluminum compound and the phosphorus compound becomes strong, and the polymerization activity tends to decrease. The measurement method of the maximum absorption wavelength (color reaction AP) of the mixed solution of the aluminum compound ethylene glycol solution and the phosphorus compound ethylene glycol solution was carried out according to the evaluation method (7) in the examples described later.

[0084] In the present invention, it is preferable to add the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound simultaneously. It is a more preferable embodiment to prepare a mixed solution by mixing the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound in the ratio added in advance and add the liquefied mixed solution. By carrying out in this manner, the effects of the present invention can be more stably exhibited. Examples of the method of pre-liquefying include a method of mixing each solution in a tank, a method of joining and mixing the pipes to which the catalyst is added in the middle, and the like. When adding to the reaction vessel, it is preferable to increase the stirring of the reaction vessel. When adding to the pipe between the 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. When an ethylene glycol solution of an aluminum compound and an ethylene glycol solution of a phosphorus compound are added separately, foreign substances caused by the aluminum compound are likely to occur in large amounts, the crystallization temperature during heating may decrease, the crystallization temperature during cooling may increase, and sufficient catalytic activity may not be obtained. 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 quickly and efficiently formed. However, when added separately, the formation of the complex of the aluminum compound and the phosphorus compound is insufficient, and there is a risk that the aluminum compound that cannot form a complex with the phosphorus compound will precipitate as a foreign substance.

[0085] In the present invention, the acid end group concentration of the oligomer when adding the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound is preferably 400 to 1500 eq / ton. More preferably, it is 500 to 1200 eq / ton. By setting the acid end group concentration of the oligomer within the above range, the activity of the polymerization catalyst can be fully exerted.

[0086] Also, in the present invention, the ratio of the hydroxyl end group (OH%) to the total end group concentration of the oligomer is preferably 45 to 70 mol%, more preferably 55 to 65 mol%. If the ratio of the hydroxyl end group of the oligomer is less than 45 mol%, the polycondensation activity may become unstable and the amount of aluminum-based foreign substances may increase. On the other hand, if the ratio of the hydroxyl end group of the oligomer exceeds 70 mol%, the polycondensation activity may decrease.

Examples

[0087] Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these example modes. The evaluation methods of the main characteristic values were based on the following methods.

[0088] 〔Evaluation Method〕 (1) Intrinsic viscosity (IV) of polyester resin The polyester resin was dissolved in a mixed solvent of phenol / 1,1,2,2-tetrachloroethane (=3 / 2; mass ratio) and measured at a temperature of 30°C.

[0089] (2) Aluminum atom content (residual amount) in the polyester resin The polyester resin was weighed into a platinum crucible, carbonized on an electric stove, and then ashed in a muffle furnace at 550°C for 8 hours. The sample after ashing was dissolved in 1.2 M hydrochloric acid to obtain a sample solution. The aluminum element concentration of the prepared sample solution was determined by high-frequency inductively coupled plasma optical emission spectrometry. Apparatus: CIROS-120 manufactured by SPECTRO Plasma output: 1400 W Plasma gas: 13.0 L / min Auxiliary gas: 2.0 L / min Nebulizer: Cross-flow nebulizer Chamber: Cyclone chamber Measurement wavelength: 167.078 nm

[0090] (3) Phosphorus atom content (residual amount) in the polyester resin The polyester resin was wet-decomposed with sulfuric acid, nitric acid, and perchloric acid and then neutralized with aqueous ammonia. Ammonium molybdate and hydrazine sulfate were added to the adjusted solution, and then the absorbance at a wavelength of 830 nm was measured using an ultraviolet-visible spectrophotometer (UV-1700 manufactured by Shimadzu Corporation). The phosphorus element concentration in the sample was determined from a calibration curve prepared in advance.

[0091] (4) Amount of aluminum-based foreign matter 30 g of polyester resin and 250 mL of a mixed solution of p-chlorophenol / tetrachloroethane (3 / 1: mass ratio) were placed in a 500 mL Erlenmeyer flask containing a magnetic stir bar, and heated and dissolved at 100 - 105 °C for 1.5 hours using a hot stirrer. The solution was filtered through a polytetrafluoroethylene membrane filter with a diameter of 47 mm and a pore size of 1.0 μm (PTFE membrane filter manufactured by Advantec, product name: T100A047A) to remove foreign substances. The effective filtration diameter was 37.5 mm. After filtration, it was continuously washed with 50 mL of chloroform, and then the filter was dried. The amount of aluminum element on the filtration surface of the membrane filter was quantified using a scanning fluorescent X-ray analyzer (ZSX100e manufactured by RIGAKU, Rh line sphere 4.0 kW). The quantification was performed on a portion with a diameter of 30 mm at the center of the membrane filter. The calibration curve of the fluorescent X-ray analysis method was determined using polyethylene terephthalate resin with a known aluminum element content, and the apparent amount of aluminum element was expressed in ppm. The measurement was carried out by measuring the intensity of the Al-Kα line under the conditions of an X-ray output of 50 kV - 70 mA, using pentaerythritol as the spectroscopic crystal and a PC (proportional counter) as the detector, and PHA (pulse height analyzer) 100 - 300. The amount of aluminum element in the PET resin for the calibration curve was quantified by high-frequency inductively coupled plasma optical emission spectrometry.

[0092] (5) Maximum absorption wavelength of the ethylene glycol solution of the phosphorus compound (color reaction P) After adding 4 mL of ethylene glycol and 0.3 mL of 1 mmol / L aqueous bismuth brown solution to a 6 mL sample bottle, 0.1 mL of the ethylene glycol solution of the phosphorus compound was added, the sample bottle was capped, and shaken for 10 seconds until the solution became uniform. After standing at room temperature (23 °C) for 10 minutes, the absorption spectrum of the sample solution was measured using an ultraviolet-visible spectrophotometer to obtain the maximum absorption wavelength. In this measurement, room temperature was defined as 15 - 30 °C, and a series of operations were carried out in a room within this temperature range. Apparatus: Ultraviolet-visible spectrophotometer UV-1800 manufactured by Shimadzu Corporation Spectral bandwidth: 1 nm Sample cell: Square cell (material: polymethyl methacrylate (PMMA), optical path length: 10 mm) Control solution: Ethylene glycol Scan range: 400 - 700 nm Scan speed setting: 0.05 sec Scan pitch: 0.2 nm Number of scans: 1 time

[0093] (6) Maximum absorption wavelength of the ethylene glycol solution of the aluminum compound (color reaction A) After adding 4 mL of ethylene glycol and 0.3 mL of 1 mmol / L Mordant Blue 13 aqueous solution to a 6 mL sample bottle, 0.1 mL of the ethylene glycol solution of the aluminum compound was added, the sample bottle was capped, and it was shaken for 10 seconds until the solution became homogeneous. After leaving this to stand at room temperature (23 °C) for 10 minutes, the absorption spectrum of the sample solution was measured using a UV-visible spectrophotometer, and the maximum absorption wavelength was determined. In this measurement, room temperature is defined as 15 - 30 °C, and a series of operations are carried out in a room within this temperature range. Device: Shimadzu Corporation UV-visible spectrophotometer UV-1800 Spectral bandwidth: 1 nm Sample cell: Square cell (material: PMMA, optical path length: 10 mm) Control solution: Ethylene glycol Scan range: 400 - 700 nm Scan speed setting: 0.05 sec Scan pitch: 0.2 nm Number of scans: 1 time

[0094] (7) Maximum absorption wavelength of the mixed solution of the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound (color reaction AP) After adding 4 mL of ethylene glycol and 0.3 mL of a 1 mmol / L aqueous solution of Mordant Blue 13 to a 6 mL sample bottle, 0.1 mL of a mixed solution of an ethylene glycol solution of an aluminum compound and an ethylene glycol solution of a phosphorus compound was added, the sample bottle was capped, and it was shaken for 10 seconds until the solution became uniform. After leaving this to stand at room temperature (23 °C) for 10 minutes, the absorption spectrum of the sample solution was measured using an ultraviolet-visible spectrophotometer, and the maximum absorption wavelength was determined. In this measurement, room temperature is defined as 15 to 30 °C, and a series of operations are carried out in a room within this temperature range. Apparatus: Ultraviolet-visible spectrophotometer UV-1800 manufactured by Shimadzu Corporation Spectral bandwidth: 1 nm Sample cell: Rectangular cell (material: PMMA, optical path length: 10 mm) Reference solution: Ethylene glycol Scan range: 400 to 700 nm Scan speed setting: 0.05 sec Scan pitch: 0.2 nm Number of scans: 1 time

[0095] (8) Back pressure increase coefficient (k) After vacuum drying the polyester resin at 140 °C for 16 hours, it was fed into a melt extruder, the pressure at the extruder outlet was controlled to 1.96 MPa, and a spinning test was carried out at a spinning temperature of 295 °C with a discharge rate of 6 g / min for 4 hours using a filter with a filter diameter of 14 mmφ. During the spinning test, the filter pressure was recorded every 30 minutes, and the increase in back pressure per unit time ΔP (MPa / hour) was calculated using the value of the pressure (MPa) 4 hours after the start of spinning and the value of the pressure (MPa) at the start of spinning. For the spinning nozzle, a nozzle having 12 orifices with a pore diameter of 0.23 mmφ and a length of 0.3 mm was used. As the filter, a filter with a configuration of a 100 mesh wire mesh, a 10 μm nylon filter, a 100 mesh wire mesh, and a 50 mesh wire mesh was used in order from the extruder outlet side. The back pressure increase coefficient k was calculated by the following formula from the increase in back pressure per unit time ΔP (MPa / hour), the flow rate Q (kg / hour), and the filtration area S (cm 2 ) k = ΔP / (Q / S) The area S was calculated from the filter diameter, and the flow rate Q was calculated from the discharge volume.

[0096] [Preparation of polycondensation catalyst solution] (1) Preparation of ethylene glycol solution of aluminum compound To an aqueous solution of basic aluminum acetate at 20 g / L, an equal amount (by volume) of ethylene glycol was charged into a mixing tank together, and after stirring at room temperature (23 °C) for several hours, water was distilled off from the system while stirring at 50 - 90 °C under reduced pressure (3 kPa) for several hours to prepare an ethylene glycol solution of aluminum compound at 20 g / L. The maximum absorption wavelength of the obtained solution was 571.6 nm.

[0097] (2) Preparation of ethylene glycol solution of phosphorus compound Formulation example 1: Used in Examples 1 - 8 and Comparative Examples 1 - 5, 7, 8 As the phosphorus compound, Irganox 1222 (manufactured by BASF) was charged into a mixing tank together with ethylene glycol, and heat-treated at 175 °C for 150 minutes while stirring under nitrogen substitution to prepare a phosphorus compound ethylene glycol solution at 50 g / L. The maximum absorption wavelength of the obtained solution was 461.2 nm. Formulation example 2: Used in Comparative Example 6 A phosphorus compound ethylene glycol solution was prepared in the same manner as in Formulation example 1, except that the heat treatment conditions were changed to 80 °C for 60 minutes in the above Formulation example 1. The maximum absorption wavelength of the obtained solution was 470.8 nm.

[0098] [Example of batch polymerization method] (Example 1) Into a 10 L stainless steel autoclave equipped with a stirrer, a polyester oligomer with an esterification rate of about 95% composed of pre-prepared high-purity terephthalic acid and ethylene glycol, and high-purity terephthalic acid were charged, and an esterification reaction was carried out at 260 °C to obtain an oligomer mixture. The obtained oligomer mixture had an acid end group concentration of 750 eq / ton and a hydroxyl end group ratio (OH%) of 59 mol%. To the obtained oligomer mixture, an ethylene glycol solution of the aluminum compound prepared by the above method and an ethylene glycol solution of the phosphorus compound were added at 10 ppm and 20 ppm as aluminum atoms and phosphorus atoms, respectively, based on the mass of the resulting polyester resin. 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 the polycondensation reaction was carried out under this condition (polycondensation time: 46 minutes) to obtain a polyester resin having an IV of 0.60 dl / g.

[0099] (Examples 2 to 5, Comparative Examples 1 to 5) In the polymerization method of Example 1, polyester resins were obtained in the same manner as in Example 1, except that an ethylene glycol solution of the aluminum compound and an ethylene glycol solution of the phosphorus compound were added in the amounts of the elements shown in Table 1 based on the mass of the resulting polyester resin.

[0100] (Comparative Example 6) A polyester resin was obtained in the same manner as in Example 2, except that the solution shown in Formulation Example 2 was used as the ethylene glycol solution of the phosphorus compound.

[0101] The physical properties of the polyester resins obtained in Examples 1 to 5 and Comparative Examples 1 to 6 are shown in Table 1. In Table 1 and Table 2 described later, the added amount and residual amount of the aluminum element are denoted as Al, the added amount and residual amount of the phosphorus element are denoted as P, and the added molar ratio and residual molar ratio of the phosphorus element to the aluminum element are denoted as P / Al.

[0102]

Table 1

[0103] Although the polyester resins of Examples 1 to 5 have small residual amounts of aluminum and phosphorus, the polycondensation time is short, and the amount of aluminum-based foreign matter is also small, so the back pressure increase coefficient is small and the quality is high. In addition, since the amount of catalyst added is small, the cost of the catalyst can be reduced. Comparative Examples 1 and 2 are preferable in that the catalyst cost is high because the amount of phosphorus compound added is large, and aluminum-based foreign substances are suppressed because the added molar ratio of phosphorus atoms to aluminum atoms is high, but the polymerization activity is low. In Comparative Example 3, although the molar ratio of phosphorus atoms to aluminum atoms is within the scope of the present invention, the polymerization activity is insufficient because the remaining amount of aluminum is too small, and the polycondensation time is long. In Comparative Examples 4 and 5, since the molar ratio of phosphorus atoms to aluminum atoms is too low, the amount of aluminum-based foreign substances in the polyester resin increases and the back pressure increase coefficient becomes large, so the quality of the polyester resin is inferior. In Comparative Example 6, the added molar ratio of phosphorus atoms to aluminum atoms is within the scope of the present invention, the polycondensation time is short, and the catalyst cost is also low. However, since the maximum absorption wavelength of the color reaction P is too large compared with Examples 1 to 5, the remaining molar ratio of phosphorus atoms to aluminum atoms is low. In addition, since the amount of aluminum-based foreign substances in the polyester resin increases and the back pressure increase coefficient becomes large, the quality of the polyester resin is inferior.

[0104] [Example of continuous polymerization method] (Example 6) A continuous polyester production apparatus comprising three continuous esterification reactors and three polycondensation reactors, and having an in-line mixer with a high-speed stirrer installed in the transfer line from the third esterification reactor to the first polycondensation reactor was continuously supplied with a slurry prepared by mixing 0.75 parts by mass of ethylene glycol with 1 part by mass of high-purity terephthalic acid, and reacted at a reaction temperature of 255°C and a pressure of 203 kPa in the first esterification reactor, a reaction temperature of 261°C and a pressure of 102 kPa in the second esterification reactor, and a reaction temperature of 261 - 263°C and a pressure of 126 kPa in the third esterification reactor to obtain 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 ratio (OH%) of 60 mol%. To the obtained oligomer, an ethylene glycol solution of the aluminum compound prepared by the above method and an ethylene glycol solution of the phosphorus compound were mixed so that the amounts of aluminum atoms and phosphorus atoms were 13 ppm and 36 ppm, respectively, based on the mass of the resulting polyester resin, and the liquefied mixture was added to the transfer line from the third esterification tank to the first polycondensation reactor using an in-line mixer. The lower-order condensation product 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 polymerization reactor to obtain a polyester resin having an IV of 0.59 dl / g. The polyester resin was extruded in a strand form, cooled in water, and then cut and pelletized.

[0105] (Examples 7, 8, Comparative Examples 7, 8) In the polymerization method of Example 6, a polyester resin was obtained in the same manner as in Example 6, except that an ethylene glycol solution of the aluminum compound and an ethylene glycol solution of the phosphorus compound were added in the amounts of catalyst elements shown in Table 2 based on the mass of the resulting polyester resin.

[0106] The physical properties, etc. of the polyester resins obtained in Examples 6 to 8 and Comparative Examples 7 and 8 are shown in Table 2.

[0107]

Table 2

[0108] The production amount ratio shown in Table 2 is the production amount per hour of Examples 6 to 8 and Comparative Example 8 expressed as a ratio based on the production amount per hour of Comparative Example 7 (with the production amount per hour of Comparative Example 7 being 1.00). If the production amount ratio is higher than 1, it indicates that the polymerization activity of the catalyst is high, and conversely, if the production amount ratio is 1 or less, it indicates that the polymerization activity of the catalyst is low. The polyester resins of Examples 6 to 8 have a higher production ratio than Comparative Examples 7 and 8, and although the remaining amounts of aluminum and phosphorus are small, the polymerization activity is improved. In addition, since the amount of aluminum-based foreign substances in the polyester resin is small, the back pressure increase coefficient is also small, and a high-quality polyester resin is obtained. In Comparative Example 8, since the residual molar ratio of phosphorus atoms to aluminum atoms is too low, the amount of aluminum-based foreign substances in the polyester resin increases, the back pressure increase coefficient becomes large, and the quality of the polyester resin is inferior.

[0109] Using the results of Examples 1 to 5 and Comparative Examples 1, 2, 4 to 6 in Table 1, the relationship between the residual molar ratio of phosphorus atoms to aluminum atoms, the amount of aluminum-based foreign substances, and the polycondensation time is shown in FIG. 1. In addition, the relationship between the maximum absorption wavelength of the catalyst mixture of the aluminum compound ethylene glycol solution and the phosphorus compound ethylene glycol solution, the amount of aluminum-based foreign substances, and the polycondensation time is shown in FIG. 2. Further, the relationship between the maximum absorption wavelength of the catalyst mixture of the aluminum compound ethylene glycol solution and the phosphorus compound ethylene glycol solution and the back pressure increase coefficient k is shown in FIG. 3. In these figures, the values of Comparative Example 3 are excluded. The reason is that in Comparative Example 3, although the molar ratio of phosphorus atoms to aluminum atoms is within the scope of the present invention, the remaining amount of aluminum is too small, so the catalytic activity is not fully exerted, and the polymerization activity is insufficient compared to other cases.

[0110] From these figures, it is clear that the scope of the present invention is critical. It is also clear that the amount of aluminum-based foreign substances and the polycondensation time are an antinomic phenomenon.

Industrial Applicability

[0111] The polyester resin of the present invention can improve the productivity of the polyester resin while keeping the catalyst cost low, and can reduce the foreign substances derived from the catalyst contained in the polyester resin. From this, it is possible to provide a clean and high-quality polyester resin, which is of great contribution to the industrial world.

Claims

1. In a method for producing a polyester resin by a batch polymerization method, an aluminum compound and a phosphorus compound are used as catalysts, and the phosphorus compound is only a dialkyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid. After the esterification reaction is completed, an ethylene glycol solution of the aluminum compound and an ethylene glycol solution of the phosphorus compound are added in amounts that satisfy the following formulas (4) to (6), and the ethylene glycol solution of the phosphorus compound is the following (7) and / or (8). A method for producing a polyester resin, characterized in that: (4) 9 ≤ Al ≤ 20 (5) 20 ≤ P ≤ 40 (6) 1.50 ≤ P / Al ≤ 2.50 [In the above formulas (4) to (6), Al is the amount (ppm) based on the mass of aluminum atoms with respect to the polyester to be produced, P is the amount (ppm) based on the mass of phosphorus atoms with respect to the polyester to be produced, and P / Al represents the molar ratio of the amount of phosphorus atoms in formula (5) to the amount of aluminum atoms added in formula (4).] (7) As the ethylene glycol solution of the phosphorus compound, a solution having a maximum absorption wavelength measured by the following color reaction P of 458.0 to 465.0 nm is used. (Here, the maximum absorption wavelength measured by the color reaction P is obtained by adding 4 mL of ethylene glycol and 0.3 mL of a 1 mmol / L aqueous solution of basic dye Bismarck Brown to a sample bottle, then adding 0.1 mL of the ethylene glycol solution of the phosphorus compound, shaking and mixing for 10 seconds until the solution becomes uniform, then standing at room temperature for 10 minutes, and then measuring the absorption spectrum using an ultraviolet-visible spectrophotometer.) (8) When preparing the ethylene glycol solution of the phosphorus compound, it is heat-treated at 175 to 196 °C for 30 to 240 minutes.

2. In a method for producing a polyester resin by a continuous polymerization method, an aluminum compound and a phosphorus compound are used as catalysts, and the phosphorus compound is only a dialkyl ester of 3,5-di-tert-butyl-4-hydroxybenzylphosphonic acid. At the outlet of the final esterification reaction tank or in the transfer line between the final esterification reaction tank and the initial polymerization reaction tank, an ethylene glycol solution of the aluminum compound and an ethylene glycol solution of the phosphorus compound are added in amounts that satisfy the following formulas (4) to (6), and the ethylene glycol solution of the phosphorus compound is the following (7) and / or (8). A method for producing a polyester resin, characterized in that: (4) 9 ≤ Al ≤ 20 (5) 20 ≤ P ≤ 40 (6) 1.50 ≤ P / Al ≤ 2.50 [In the above formulas (4) to (6), Al is the amount (ppm) based on the mass of aluminum atoms with respect to the polyester to be produced, P is the amount (ppm) based on the mass of phosphorus atoms with respect to the polyester to be produced, and P / Al represents the molar ratio of the amount of phosphorus atoms in formula (5) to the amount of aluminum atoms added in formula (4).] (7) As the ethylene glycol solution of the phosphorus compound, use a solution in which the maximum absorption wavelength measured by the following color reaction P is 458.0 to 465.0 nm. (Here, the maximum absorption wavelength measured by the color reaction P is obtained by adding 4 mL of ethylene glycol and 0.3 mL of a 1 mmol / L aqueous solution of Bismarck Brown, which is a basic dye, to a sample bottle, then adding 0.1 mL of the ethylene glycol solution of the phosphorus compound and shaking for 10 seconds until the solution becomes uniform, then allowing it to stand at room temperature for 10 minutes, and then measuring the absorption spectrum using an ultraviolet-visible spectrophotometer.) (8) When preparing the ethylene glycol solution of the phosphorus compound, perform heat treatment at 175 to 196 °C for 30 to 240 minutes.

3. The method for producing a polyester resin according to claim 1 or 2, characterized in that, as the ethylene glycol solution of the aluminum compound, use a solution in which the maximum absorption wavelength measured by the following color reaction A is 562.0 to 572.0 nm. (Here, the maximum absorption wavelength measured by the color reaction A is obtained by adding 4 mL of ethylene glycol and 0.3 mL of a 1 mmol / L aqueous solution of Mordant Blue 13, which is an acidic dye, to a sample bottle, then adding 0.1 mL of the ethylene glycol solution of the aluminum compound and shaking for 10 seconds until the solution becomes uniform, then allowing it to stand at room temperature for 10 minutes, and then measuring the absorption spectrum using an ultraviolet-visible spectrophotometer.)

4. The method for producing a polyester resin according to any one of claims 1 to 3, characterized in that, as the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound, use a solution in which the maximum absorption wavelength measured by the following color reaction AP of the mixed solution obtained by mixing the ethylene glycol solution of the aluminum compound and the ethylene glycol solution of the phosphorus compound in the amount ratio added to the polyester resin production process is 559.5 to 561.5 nm. (Here, the maximum absorption wavelength measured by the color reaction AP is obtained by adding 4 mL of ethylene glycol and 0.3 mL of an aqueous solution of 1 mmol / L Mordant Blue 13, which is an acidic dye, to a sample bottle, then adding 0.1 mL of a mixed solution of an ethylene glycol solution of an aluminum compound and an ethylene glycol solution of a phosphorus compound, shaking and mixing for 10 seconds until the solution becomes uniform, then allowing it to stand at room temperature for 10 minutes, and then measuring the absorption spectrum using an ultraviolet-visible spectrophotometer.)

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