JP2006291033A - Method for producing polyester using only trace amount of titanium compound as catalyst - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a polyester having good hue in which only a trace amount of titanium compound is used as a catalyst. <P>SOLUTION: The method for producing a polyethylene terephthalate having ≤1.0 Col-b value comprises using a polycondensation catalyst composed of a titanium compound component containing at least one kind of material selected from a group consisting of a product obtained by reacting a titanium compound represented by general formula (I) (wherein R<SP>1</SP>, R<SP>2</SP>, R<SP>3</SP>and R<SP>4</SP>are each the same or different and they are each an alkyl group or a phenyl group and m is an integer of 1-4 and when m is 2, 3 or 4, two, three or four R<SP>2</SP>and R<SP>3</SP>may be each the same or different) with an aromatic polyhydric carboxylic acid represented by general formula (II) (wherein n is an integer of 2-4) or its anhydride so that number of moles of titanium atom to ton of polyethylene terephthalate produced becomes ≤0.031 mol and ≥0.020 mol. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing a hueable polyester using only a titanium compound as a catalyst.

  Polyester, particularly polyethylene terephthalate (hereinafter abbreviated as PET), is widely used by being molded into fibers, films, industrial resins, bottles, cups, trays, etc. because of its excellent mechanical and chemical properties. Yes.

  Usually, polyester is produced from aromatic dicarboxylic acids such as terephthalic acid and aliphatic diols such as ethylene glycol as raw materials. Specifically, first, a low-order condensate (ester low polymer) is formed by an esterification reaction of an aromatic dicarboxylic acid and an aliphatic diol, and then this low-order condensate is formed in the presence of a polycondensation catalyst. It is deglycolized (liquid phase polycondensation) to increase the molecular weight. In some cases, solid state polycondensation is performed to further increase the molecular weight.

  In the polyester production method, an antimony compound, a germanium compound, or the like is conventionally used as a polycondensation catalyst. However, polyethylene terephthalate produced using an antimony compound as a catalyst is inferior to polyethylene terephthalate produced using a germanium compound as a catalyst in terms of transparency and heat resistance. Further, it is known that the content of acetaldehyde in the obtained polyester is still high, and there is a demand for reducing this content.

  Moreover, since the germanium compound is quite expensive, there is a problem that the production cost of the polyester is increased. For this reason, in order to reduce the production cost, a process of recovering and reusing the germanium compound scattered during the polycondensation has been studied.

  By the way, titanium is known to be an element having an action of promoting ester polycondensation reaction, and titanium alkoxide, titanium tetrachloride, titanyl oxalate, orthotitanic acid and the like are known as polycondensation catalysts. Many studies have been conducted in order to use a titanium compound as a polycondensation catalyst.

  However, when a conventional titanium-based catalyst is used as a polycondensation catalyst, there is a problem that the obtained polyester is remarkably colored in yellow although it is more active than antimony compounds and germanium compounds.

  In order to solve the above-mentioned coloring problem, it is generally performed to add a cobalt compound to polyester to suppress yellowing. Certainly, the hue (b value) of the polyester can be improved by adding a cobalt compound, but the problem that the melting heat stability of the polyester is lowered and the polymer is easily decomposed by adding the cobalt compound. There is.

  Further, as other titanium compounds, use of titanium hydroxide as a catalyst for producing a polyester (for example, see Patent Document 1) and use of α-titanic acid as a catalyst for producing a polyester (for example, see Patent Document 2). It is disclosed. However, in the former method, powdering of titanium hydroxide is not easy. On the other hand, in the latter method, α-titanic acid is easily changed in quality, so its storage and handling are not easy. Not suitable for. Furthermore, it is difficult to obtain a polymer having a good color tone (b value) by these methods.

  In addition, the use of a product obtained by reacting a titanium compound and a phosphite as a polyester production catalyst is disclosed (for example, see Patent Document 3).

  Certainly, according to these methods, although the melt heat stability of the polyester is improved to some extent, the color tone of the obtained polymer is not sufficient, and therefore further improvement of the polymer color tone is desired.

  Furthermore, it has also been proposed to use a complex of a titanium compound and a phosphorus compound as a polyester production catalyst (see, for example, Patent Document 4). Certainly, this method also improves the heat stability of melting to some extent, but the color tone of the resulting polymer is not sufficient.

  A catalyst obtained by reacting a titanium compound with an alkaline earth metal compound has also been proposed (see, for example, Patent Document 5). However, even with this method, the hue of the polyester is not sufficient.

  In addition, a phosphorus compound, a metal compound of Groups 1A and 2A of the periodic table, and in some cases, a titanium compound is added in an amount of 0.02 to 1 mole as titanium atoms per ton of polyester resin in the presence of germanium. A method of using it as a condensation catalyst has also been proposed (see, for example, Patent Document 6). However, metal compounds having transesterification activity such as those of Group 1A and Group 2A of the Periodic Table may cause coloring, aggregated foreign matter, and acetaldehyde by-product, and should be added to polyester as little as possible. (For example, refer nonpatent literature 1).

Japanese Patent Publication No. 48-2229 Japanese Patent Publication No. 47-26597 JP 58-38722 A JP 7-138354 A JP 2000-109552 A JP 2002-226562 A Saturated Polyester Resin Handbook, Kazuo Yuki, Nikkan Kogyo Shimbun, December 22, 1981, 1st edition, 1 issue, 99 pages and 148 pages

  The subject of this invention is providing the manufacturing method of polyester with favorable hue which uses only a very small amount of titanium compounds as a catalyst.

  In order to solve the above problems, the present invention is a product obtained by reacting a titanium compound represented by the following general formula (I) and an aromatic polyvalent carboxylic acid represented by the following general formula (II) or an anhydride thereof. The polycondensation catalyst comprising a titanium compound component containing at least one selected from the group consisting of the product is such that the number of moles of titanium atoms is 0.020 mol or more and 0.031 mol or less with respect to 1 ton of polyethylene terephthalate produced. A method for producing polyethylene terephthalate having a Col-b value of 1.0 or less is provided.

［上記式中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４はそれぞれ同一若しくは異なって、アルキル基又はフェニル基を示し、ｍは１〜４の整数を示し、かつｍが２、３又は４の場合、２個、３個又は４個のＲ^２及びＲ^３は、それぞれ同一であっても異なっていてもどちらでもよい。］

[Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents an alkyl group or a phenyl group, m represents an integer of 1 to 4, and m represents 2, 3 or 4] In this case, 2, 3 or 4 R ² and R ³ may be the same or different from each other. ]

［上記式中、ｎは２〜４の整数を表わす。］

[In the above formula, n represents an integer of 2 to 4. ]

  By the method of the present invention, polyethylene terephthalate having a good hue can be produced using only a titanium compound as a catalyst.

  In the present invention, the polyester production catalyst contains the titanium compound component. Hereinafter, a production method for efficiently obtaining the polyester production catalyst of the present invention will be described. As a polycondensation catalyst for the titanium compound used in the present invention, a titanium compound represented by the following general formula (I) and an aromatic polyvalent carboxylic acid represented by the following general formula (II) or an anhydride thereof are reacted. And a titanium compound component containing at least one selected from the group consisting of the products.

［上記式中、Ｒ^１、Ｒ^２、Ｒ^３及びＲ^４はそれぞれ同一若しくは異なって、アルキル基又はフェニル基を示し、ｍは１〜４の整数を示し、かつｍが２、３又は４の場合、２個、３個又は４個のＲ^２及びＲ^３は、それぞれ同一であっても異なっていてもどちらでもよい。］

[Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents an alkyl group or a phenyl group, m represents an integer of 1 to 4, and m represents 2, 3 or 4] In this case, 2, 3 or 4 R ² and R ³ may be the same or different from each other. ]

［上記式中、ｎは２〜４の整数を表わす。］

[In the above formula, n represents an integer of 2 to 4. ]

Specific examples of R ^{1 to} R ⁴ include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, a tert-butyl group, a hexyl group, and a phenyl unit. . Although m is an integer of 1-4, the integer of 1-3 is preferable. M is an integer of 2 to 4, and an integer of 2 to 3 is preferable.

  Here, as the titanium compound represented by the general formula (I), specifically, tetraethoxy titanium, tetraisopropoxy titanium, tetra-n-propoxy titanium, tetra-n-butoxy titanium, tetraphenoxy titanium, octaalkyl Trititanate or hexaalkyl dititanate is preferably used.

  In addition, the aromatic polyvalent carboxylic acid represented by the general formula (II) to be reacted with the titanium compound or an anhydride thereof includes phthalic acid, trimellitic acid, hemimellitic acid, pyromellitic acid, or an anhydride thereof. Is mentioned. These have a function of stabilizing the titanium compound of the above general formula (I), which is generally unstable to moisture and heat, in a solvent, and the amount of addition is not particularly limited. 0.5-4.0 times mole amount is preferable and it is still more preferable to add 1.0-2.0 times mole amount. When it is within this range, the above stabilizing effect is exhibited to the maximum, and there is no problem in the quality of the finally obtained polyester.

  In the case of reacting the titanium compound with an aromatic polyvalent carboxylic acid or an anhydride thereof, a part or all of the aromatic polyvalent carboxylic acid or an anhydride thereof is dissolved in a solvent, and the titanium compound is dissolved in the mixed solution. It is carried out by dripping and heating at a temperature of 0-200 ° C. for at least 30 minutes, preferably at a temperature of 30-150 ° C. for 40-90 minutes. There is no restriction | limiting in particular about the reaction pressure in this case, A normal pressure is enough. As a solvent for dissolving the aromatic polyvalent carboxylic acid or its anhydride, any of ethanol, ethylene glycol, trimethylene glycol, tetramethylene glycol, benzene, xylene and the like can be used as desired.

  Here, the reaction molar ratio between the titanium compound and the aromatic polyvalent carboxylic acid or its anhydride is not particularly limited, but if the proportion of the titanium compound is too high, the color tone of the resulting polyester deteriorates, or the softening point. In contrast, if the proportion of the titanium compound is too low, the polycondensation reaction may be difficult to proceed. For this reason, it is preferable that the reaction molar ratio of a titanium compound and aromatic polyvalent carboxylic acid or its anhydride shall be in the range of 2/1-2/5. Also, there is no particular limitation as long as the above titanium compound can be reacted with the aromatic polyvalent carboxylic acid or its anhydride under other conditions.

  The product may be present during the polycondensation reaction. For this reason, the catalyst may be added in any step such as a raw material slurry preparation step, an esterification step, a liquid phase polycondensation step, etc. However, the addition amount of the catalyst must be used so that the number of moles of titanium atoms is 0.020 mol or more and 0.031 mol or less with respect to 1 ton of the generated polyethylene terephthalate. In addition, the Col-b value needs to be 1.0 or less. When the number of moles of titanium atoms exceeds 0.031 with respect to 1 ton of polyethylene terephthalate produced, the yellowness of the polymer hue becomes strong and the Col-b value exceeds 1.0, which is below 0.020. Then, polycondensation is insufficient and a polymer chip with a good shape cannot be obtained.

  Moreover, you may mix | blend antioxidant, a ultraviolet absorber, a flame retardant, a fluorescent whitening agent, a matting agent, a color adjusting agent, an antifoamer, and other additives.

  Furthermore, in order to help improve the hue of the polyester obtained, in the production stage of the reactive polyester, organic blue pigments such as azo, triphenylmethane, quinoline, anthraquinone, phthalocyanine, etc. and other than inorganic It is also possible to add the color adjusting agent. Furthermore, when manufacturing these polyethylene terephthalates, you may use another additive, for example, a coloring agent, an antioxidant, a ultraviolet absorber, an antistatic agent, a flame retardant, etc. as needed.

  In the present invention, a phosphorus compound may be added as a stabilizer. Examples of the phosphorus compound include trimethyl phosphate, triethyl phosphate, triphenyl phosphate, triethyl phosphonoacetate, triphenyl phosphite, trisdodecyl phosphite, methyl acid phosphate, dibutyl phosphate, monobutyl phosphate, phosphoric acid, phosphorous acid, next Phosphorous acid, phenylphosphonic acid polyphosphoric acid, methylphosphonic acid, ethylphosphonic acid, propylphosphonic acid, isopropylphosphonic acid, butylphosphonic acid, tolylphosphonic acid, xylylphosphonic acid, biphenylphosphonic acid, naphthylphosphonic acid, anthrylphosphonic acid 2-carboxyphenylphosphonic acid, 3-carboxyphenylphosphonic acid, 4-carboxyphenylphosphonic acid, 2,3-dicarboxyphenylphosphonic acid, 2,4-di Ruboxyphenylphosphonic acid, 2,5-dicarboxyphenylphosphonic acid, 2,6-dicarboxyphenylphosphonic acid, 3,4-dicarboxyphenylphosphonic acid, 3,5-dicarboxyphenylphosphonic acid, 2,3, 4-tricarboxyphenylphosphonic acid, 2,3,5-tricarboxyphenylphosphonic acid, 2,3,6-tricarboxyphenylphosphonic acid, 2,4,5-tricarboxyphenylphosphonic acid, 2,4,6- Tricarboxyphenylphosphonic acid, monomethyl phosphate, monoethyl phosphate, monotrimethyl phosphate, mono-n-butyl phosphate, monohexyl phosphate, monoheptyl phosphate, monononyl phosphate, monodecyl phosphate, monododecyl phosphate, monophenyl phosphate Fate, monobenzyl phosphate, mono (4-dodecyl) phenyl phosphate, mono (4-methylphenyl) phosphate, mono (4-ethylphenyl) phosphate, mono (4-propylphenyl) phosphate, mono (4-dodecylphenyl) phosphate , Monotolyl phosphate, monoxyl phosphate, monobiphenyl phosphate, mononaphthyl phosphate, monoanthryl phosphate and the like.

  Next, the manufacturing method of the polyethylene terephthalate using the titanium compound catalyst of this invention is demonstrated. In the present invention, in producing polyethylene terephthalate, it can be produced by polycondensation of terephthalic acid, ethylene glycol, and an appropriate amount of diethylene glycol according to the intended physical properties.

  Examples of the acid component include phthalic acid, isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, adipic acid, sebacic acid, azelaic acid, decanedicarboxylic acid and other aliphatic dicarboxylic acids, cyclohexanedicarboxylic acid Or an ester-forming derivative thereof can be used as a copolymerization component. Examples of the diol component include trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexanemethylene glycol, dodecamethylene glycol, cyclohexanedimethanol, polyethylene glycol and other alicyclic glycols, bisphenol, hydroquinone, and 2,2-bis. Aromatic diols such as (4-β-hydroxyethoxyphenyl) propanes can be used as raw materials. Furthermore, polyfunctional compounds such as trimesic acid, trimethylolethane, trimethylolpropane, trimethylolmethane, pentaerythritol, trimellitic acid, and pyromellitic acid can be used as the copolymerization component.

  First, when producing a polyester using the above raw materials, an oligomer obtained by directly esterifying terephthalic acid and ethylene glycol is subjected to a polycondensation reaction using the polyester polycondensation catalyst of the present invention.

  For example, the direct esterification method specifically prepares a slurry containing terephthalic acid and ethylene glycol. Such a slurry usually contains 1.1 to 1.6 mol, preferably 1.2 to 1.4 mol, of ethylene glycol with respect to 1 mol of terephthalic acid. This slurry is continuously supplied to the esterification reaction step.

  The esterification reaction is preferably carried out in a single stage without allowing the reactants to circulate, or a method in which two or more esterification reaction groups are connected in series, both of which are under conditions where ethylene glycol is refluxed. It is carried out while removing water produced by the reaction from the system with a rectification column.

  The reaction conditions in the case of carrying out esterification continuously in one stage without allowing the reactants to circulate are usually a reaction temperature of 240 to 280 ° C., preferably 250 to 270 ° C., and a reaction pressure of normal pressure to 0.00. The reaction is carried out under the condition of 3 MPa, and the reaction is desirably carried out until the esterification rate is usually 90% or more, preferably 95% or more. By this esterification step, an esterification reaction product (oligomer) of terephthalic acid and ethylene glycol is obtained, and the degree of polymerization of this oligomer is about 4-10. The oligomer obtained in the esterification step as described above is then supplied to a polycondensation (liquid phase polycondensation) step.

  Next, in the liquid phase polycondensation step, in the presence of the polycondensation catalyst described above, the oligomer obtained in the esterification step is heated under reduced pressure to a temperature not lower than the melting point of the polyester (usually 240 to 280 ° C.). To polycondense. This polycondensation reaction is preferably carried out while distilling off unreacted ethylene glycol and ethylene glycol generated by polycondensation outside the reaction system.

  The polycondensation reaction may be performed in one tank or may be performed in a plurality of tanks. For example, when the polycondensation reaction is performed in two stages, the polycondensation reaction in the first tank has a reaction temperature of 245 to 290 ° C., preferably 260 to 280 ° C., and a pressure of 100 to 1 kPa, preferably 50 to The polycondensation reaction is carried out under the condition of 2 kPa, and the polycondensation reaction in the final second tank is a reaction temperature of 265 to 300 ° C., preferably 270 to 290 ° C., and a reaction pressure of usually 1000 to 10 Pa, preferably 500 to 30 Pa. Done under.

  In this way, a polyester can be produced using the catalyst for producing a polyester of the present invention. The polyester obtained in this polycondensation step is usually extruded in a molten state, cooled, and then granulated (chips). And The intrinsic viscosity of the obtained polyester is 0.40 to 0.80 dL / g, preferably 0.50 to 0.70 dL / g.

  After the polyethylene terephthalate obtained in this way is pelletized, it may be further subjected to polycondensation in a solid phase polymerization step as necessary. Any known method can be used for the solid phase polymerization method. May be. When the granular polyester supplied to the solid phase polycondensation reaction is preliminarily crystallized by heating to a temperature lower than the temperature in the case of performing solid phase polycondensation, It is preferable because the fusion between the granular polyesters and / or the inner wall of the reaction vessel can be suppressed during the polymerization reaction.

  Such a precrystallization step can be performed by heating the granular polyester in a dry state to a temperature of usually 120 to 200 ° C., preferably 130 to 180 ° C. for 1 minute to 4 hours. Such pre-crystallization can also be performed by heating the granular polyester at a temperature of 120 to 200 ° C. for 1 minute or more in a steam atmosphere, a steam-containing inert gas atmosphere, or a steam-containing air atmosphere. .

  The precrystallized polyester desirably has a crystallinity of 20 to 50%. The so-called polyester solid-phase polycondensation reaction does not proceed by this precrystallization treatment, and the intrinsic viscosity of the precrystallized polyester is almost the same as the intrinsic viscosity of the polyester after polycondensation. The intrinsic viscosity difference before and after the formation is usually 0.06 dL / g or less.

  The solid phase polycondensation step comprises at least one stage, a temperature of 190 to 230 ° C., preferably 195 to 225 ° C., and a pressure of 200 kPa to 1 kPa, preferably from normal pressure to 10 kPa, under conditions of nitrogen, argon, It is performed under an inert gas atmosphere such as carbon dioxide. Nitrogen gas is desirable as the inert gas used.

  The granular polyester obtained through such a solid-phase polycondensation step may be subjected to water treatment as necessary. This water treatment is carried out by treating the granular polyester with water, steam, steam-containing inert gas, steam-containing. It is performed by contacting with air or the like.

  The production process of the polyester as described above can be performed by any of a batch type, a semi-continuous type, and a continuous type. In particular, polyethylene terephthalate that undergoes solid phase polycondensation is often used in bottles and the like, and therefore has an intrinsic viscosity of 0.70 to 1.0 dL / g and a cyclic trimer in polyethylene terephthalate. It is preferable that the content is 0.5 wt% or less and the acetaldehyde content is 5 ppm or less.

  In addition, since the cyclic trimer and acetaldehyde in polyethylene terephthalate are usually reduced in the solid phase polycondensation step, the intrinsic viscosity of the melt condensation before the solid phase polycondensation and the conditions of the solid phase polycondensation should be adjusted. It can respond.

EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention does not receive any limitation by this. In addition, each value in an Example was calculated | required with the following method.
1) Intrinsic viscosity ([η]):
After 0.6 g of polyethylene terephthalate was dissolved by heating in 50 cc of o-chlorophenol, it was once cooled and calculated from the solution viscosity of the solution measured at 35 ° C. using an Ubbelohde viscometer.
2) Hue (Col)
The granular polymer sample was heat-treated in a dryer at 160 ° C. for 90 minutes to crystallize, and then measured with a CM-7500 type color machine manufactured by Color Machine Co., Ltd. Yellowness was evaluated by the Col-b value.
3) Diethylene glycol (DEG) content The sample was decomposed with hydrazine hydrate and measured by gas chromatography (GC).

[Reference Example 1]
In a reactor equipped with a stirrer, 919 parts by weight of ethylene glycol and 80 parts by weight of trimellitic anhydride were mixed and stirred in a nitrogen atmosphere, and 71 parts by weight of tetra-n-butoxytitanium was slowly added gradually to obtain a transparent An ethylene glycol solution of a titanium compound (hereinafter referred to as TMT catalyst) was obtained. The reaction molar ratio of tetra-n-butoxytitanium and trimellitic anhydride was ½.

[Example 1]
Production of polyester:
In a reactor in which 225 parts of oligomers have been retained in advance, 179 parts of high-purity terephthalic acid and 95 parts of ethylene glycol were mixed under conditions of 255 ° C. and normal pressure in a nitrogen atmosphere under stirring. The prepared slurry was supplied at a constant rate, and the esterification reaction was completed for 4 hours while water and ethylene glycol generated in the reaction were distilled out of the system to complete the reaction. The esterification rate at this time was 98% or more, and the polymerization degree of the produced oligomer was about 5 to 7.

  225 parts of the oligomer obtained by the esterification reaction was transferred to a polycondensation reaction tank, and the TMT catalyst obtained in Example 1 was used as a polycondensation catalyst in an amount such that the titanium atom was 0.031 mol with respect to polyethylene terephthalate. And put it in. Subsequently, the reaction temperature in the system is increased from 255 to 280 ° C., and the reaction pressure is gradually increased and reduced from normal pressure to 60 Pa, respectively, and the polycondensation reaction is carried out while removing water and ethylene glycol generated in the reaction from the system. went.

  The progress of the polycondensation reaction was confirmed without monitoring the load on the stirring blades in the system, and the reaction was terminated when the desired degree of polymerization was reached. Thereafter, the reaction product in the system was continuously extruded in a strand form from the discharge part, cooled and cut to obtain a granular pellet of about 3 mm. The polycondensation reaction time at this time was 189 minutes. The quality of the obtained polyethylene terephthalate is shown in Table 1.

[Example 2]
In Example 2, the same operation was performed except that the TMT catalyst was used in an amount such that the titanium atom was 0.020 mol relative to polyethylene terephthalate. The polycondensation reaction time at this time was 210 minutes. The quality of the produced polyethylene terephthalate is shown in Table 1.

[Comparative Example 1]
In Example 2, the same operation was performed except that the TMT catalyst was charged and used in such an amount that the titanium atom was 0.052 mol relative to polyethylene terephthalate. The polycondensation reaction time at this time was 143 minutes. The quality of the produced polyethylene terephthalate is shown in Table 1.

[Comparative Example 2]
In Example 2, the same operation was carried out except that the TMT catalyst was charged and used in such an amount that the titanium atom was 0.016 mol relative to polyethylene terephthalate. Since the polycondensation reaction at this time did not proceed sufficiently, the polymer was discharged without cutter treatment.

[Comparative Example 3]
In Example 2, the same operation was performed except that tetrabutoxy titanium was used instead of the TMT catalyst. The polycondensation reaction time at this time was 151 minutes. The quality of the produced polyethylene terephthalate is shown in Table 1.

[Comparative Example 4]
In Example 2, the same operation was performed except that tetramethoxy titanium was used instead of the TMT catalyst. The polycondensation reaction time at this time was 154 minutes. The quality of the produced polyethylene terephthalate is shown in Table 1.

  According to the method of the present invention, polyethylene terephthalate having a good hue can be obtained using only a very small amount of a titanium compound as a catalyst, so that its industrial significance is great.

Claims (1)

At least one selected from the group consisting of a product obtained by reacting a titanium compound represented by the following general formula (I) and an aromatic polycarboxylic acid represented by the following general formula (II) or an anhydride thereof: A polycondensation catalyst comprising a titanium compound component is used so that the number of moles of titanium atoms is 0.020 mol or more and 0.031 mol or less with respect to 1 ton of polyethylene terephthalate produced, and the Col-b value is 1.0 or less Of manufacturing polyethylene terephthalate.

[Wherein R ¹ , R ² , R ³ and R ⁴ are the same or different and each represents an alkyl group or a phenyl group, m represents an integer of 1 to 4, and m represents 2, 3 or 4] In this case, 2, 3 or 4 R ² and R ³ may be the same or different from each other. ]

[In the above formula, n represents an integer of 2 to 4. ]