JPH0350770B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a polyester whose main repeating unit is ethylene terephthalate, which has highly improved electrostatic adhesion and good heat resistance. Saturated linear polyester, represented by polyethylene terephthalate, has excellent mechanical properties, heat resistance, weather resistance, electrical insulation, and chemical resistance, so it is used in a wide range of fields such as packaging, photography, electrical applications, and magnetic tape. Used a lot. Polyester films are usually obtained by melt-extruding polyester and then biaxially stretching it. In this case, in order to increase the uniformity of the film thickness and the casting speed, when the sheet material melted and extruded from the extrusion nozzle is rapidly cooled on the surface of the rotating cooling drum, it is necessary to ensure that the sheet material and the drum surface are in close contact with each other. We must improve our sexuality. As a method of increasing the adhesion between the sheet-like material and the drum surface, a wire-shaped electrode is installed between the extrusion die and the rotating cooling drum, and a high voltage is applied to deposit static electricity on the top surface of the unsolidified sheet-like material. It is known that a method of rapidly cooling the sheet while closely contacting the surface of the cooling body (hereinafter referred to as electrostatic adhesion casting method) is effective. Uniformity of film thickness is an extremely important characteristic for film quality, and film productivity is directly dependent on casting speed, so increasing the casting speed is extremely important to improve productivity. Therefore, great efforts are being made to improve electrostatic adhesion. It is known that increasing the amount of charge on the surface of a sheet-like object is an effective means for improving electrostatic adhesion. In addition, it is known that in order to increase the amount of charge on the surface of a sheet material in the electrostatic adhesion casting method, it is effective to modify the polyester raw material used in the production of polyester film to lower its specific resistance. ing. The present inventors have already discovered that by adding a Ca compound or Mg compound, an alkali metal compound, and a P compound in a specific amount ratio at a specific time in the polyester manufacturing process, the specific resistance of the polyester raw material can be lowered and a high level of static electricity can be achieved. We are proposing a method that can provide adhesion. It is true that these methods are effective means for imparting electrostatic adhesion, but in order to achieve a high degree of electrostatic adhesion, the atomic ratio between the metal compound and the P compound (hereinafter referred to as metal/P compound) must be adjusted. It is necessary to increase the P ratio. Increasing the metal/P ratio is an extremely effective means of improving electrostatic adhesion, but on the other hand, the thermal stability of polyester decreases in proportion to the metal/P ratio, making it difficult to achieve high electrostatic adhesion. In order to ensure this, it is necessary to tolerate a certain degree of decrease in thermal stability. However, if the heat resistance of the polyester deteriorates, it becomes difficult to melt and reuse the edges of the film and non-standard film produced during the stretching process, which is not preferable. Therefore, the present inventors have conducted intensive studies on a method for producing a polyester whose main repeating unit is ethylene terephthalate, which improves the above-mentioned drawbacks, has highly improved electrostatic adhesion, and has good heat resistance. This has led to the present invention. That is, the first invention of the present invention provides that when producing a polyester from a dicarboxylic acid containing terephthalic acid as a main component or a terephthal-forming derivative thereof and a glycol containing ethylene glycol as a main component in the presence of a Ca and/or Mg compound, This is a method for producing polyester, which is characterized in that a P compound that does not contain metal atoms is divided into two or more portions, and the amount added at the first time is less than 50 mol% of the total amount of P compound added. A second invention of the present invention is, in the first invention,
This is a method for producing polyester, characterized in that at least one compound selected from Li, Na, K, Mn, Zn and Zr compounds is used in combination. The polyester of the present invention has 80 repeating units.
More than mol% is composed of ethylene terephthalate, and other copolymerized components include isophthalic acid, P-β-oxyethoxybenzoic acid, 2,6-
Naphthalenedicarboxylic acid, 4,4'-dicarboxyldiphenyl, 4,4'-dicarboxylbenzophenone, bis(4-carboxylphenyl)
Examples include dicarboxylic acid components such as ethane, adipic acid, sebacic acid, and 5-sodium sulfoisophthalic acid. Further, as the glycol component, propylene glycol, butanediol, neopentyl glycol, diethylene glycol, cyclohexanedimethanol, ethylene oxide adduct of bisphenol A, etc. can be arbitrarily selected and used. In addition, small amounts of amide bonds, urethane bonds, ether bonds, carbonate bonds, etc. may be included as copolymer components. Ca compounds, Mg compounds, Li used in the present invention
Compound, Na compound, K compound, Mn compound, Zn
Any compound and Zr compound can be used as long as they are soluble in the reaction system. For example, Ca compounds include lower fatty acid salts such as calcium hydride, calcium oxide, and calcium acetate, and alkoxides such as calcium methoxide, and Mg compounds include lower fatty acid salts such as magnesium hydride and magnesium acetate. , alkoxides such as magnesium methoxide, etc. Li compound,
Examples of Na compounds and K compounds include carboxylates, carbonates, hydrides, and alkoxides of Li, Na, and K. Specifically, lithium acetate,
Sodium acetate, potassium acetate, lithium benzoate, sodium benzoate, potassium benzoate, sodium bicarbonate, potassium bicarbonate, lithium hydride, sodium hydride, potassium hydride, lithium methoxide, sodium methoxide, potassium methoxide, Examples include lithium ethoxide, sodium ethoxide, potassium ethoxide, and the like. In addition, Mn compounds and Zn compounds include organic acid salts such as manganese acetate, zinc acetate, manganese benzoate and zinc benzoate, halides such as manganese chloride and zinc chloride, alkoxides such as manganese methoxide and zinc methoxide,
These include acetylacetonate salts of manganese and zinc, and examples of Zr compounds include organic acid salts such as zirconyl acetate, inorganic acid salts such as zirconyl chloride, and alkoxides such as tetra-n-butylzirconate. Examples of the metal-free P compound used in the present invention include phosphoric acid, phosphorous acid, phosphonic acid, and derivatives thereof. Specific examples include phosphoric acid, phosphoric acid trimethyl ester, phosphoric acid triethyl ester, Phosphate tributyl ester, phosphate triphenyl ester, phosphate monomethyl ester, phosphate dimethyl ester, phosphate monobutyl ester, phosphate dibutyl ester, phosphorous acid, phosphite trimethyl ester, phosphite triethyl ester, phosphorous acid tributyl ester,
Methylphosphonic acid, methylphosphonic acid dimethyl ester, ethylphosphonic acid dimethyl ester, phenylphosphonic acid dimethyl ester, phenylphosphonic acid diethyl ester, phenylphosphonic acid diphenyl ester, etc., and these may be used alone or Two or more types may be used in combination. The greatest feature of the present invention is that the P compound is added to the polyester manufacturing process in two or more portions. If the P compound is not added in parts, it is necessary to increase the metal/P ratio in order to impart high electrostatic adhesion, which is not preferable because the heat resistance of the polyester decreases. On the other hand, if the P compound is added in parts, a high level of electrostatic adhesion can be obtained even if the metal/P ratio is lowered, thereby imparting a high level of electrostatic adhesion without reducing the heat resistance of polyester. It becomes possible to do so. The method of adding the P compound in portions can be carried out by shifting the addition time when carried out batchwise, or by changing the addition location when carried out continuously. If it is carried out continuously, it can be carried out by increasing the number of reaction vessels, but this increases the equipment cost, so dividing the interior of the reaction vessel is necessary.
A method in which it is added to each divided portion is preferred. Alternatively, a method of line mixing may be adopted at the connecting portion between the reaction vessels. The number of divisions is not particularly limited as long as it is two or more times, but increasing the number of divisions will complicate the addition program when using the batch method, and will complicate the manufacturing equipment when using the continuous method. Since this increases equipment costs, it is particularly preferable to divide the process into two times. The division ratio of the amount of P compound added is preferably such that the amount added at the first time is 50% or less of the total amount added, particularly preferably 30% or less. By using such a dividing ratio, the effect of dividing and adding is more clearly expressed. The total amount of the P compound added is preferably in the range of 1.0 to 10, particularly preferably 1.2 to 3.0, as the final metal/P ratio remaining in the polyester. If it is less than 1.0, electrostatic adhesion deteriorates, which is not preferable. On the other hand, if it exceeds 10, the heat resistance and resin color will deteriorate, which is not preferable. Note that the metal here refers to the total amount of the metal compounds mentioned above, and in the case of an alkali metal, it is a value calculated assuming that 1/2 mole corresponds to 1 mole of P. Regarding the timing of addition of the P compound, it is preferable that the second and subsequent additions be performed after the addition of the Ca compound and the Mg compound. With this embodiment, the effect of adding the P compound in portions is more clearly expressed. 1st
There is no particular limitation on the timing of adding the P compound for the first time.
It may be added before, at the same time, or after the Ca compound or the Mg compound, but when using the Ca compound, it is preferable to add the P compound first, and when using the Mg compound, it is preferable to add the P compound after. The reason why a high level of electrostatic adhesion can be imparted even if the metal/P ratio is lowered by adding the P compound in portions as described above is unknown, but adding the P compound in portions is not clear. This is thought to be caused by a slight change in the composition of the three reaction products of Ca, Mg compounds, P compounds, and oligomers, and an increase in the concentration of the conductive compound produced. In the present invention, in order to impart high electrostatic adhesion, Ca or
It is essential to add one of the Mg compounds. The amount of these Ca and Mg compounds added is 30 to 30% as metal atoms to the polyester produced.
400 ppm is preferred, and 50 to 200 ppm is particularly preferred. Addition of metal compounds other than Ca and Mg compounds is essential when implementing the so-called internal particle method, which imparts slipperiness by producing precipitated particles during the polyester manufacturing process. The preferred amount to be added should be appropriately selected depending on the concentration of particles to be precipitated, particle size distribution, etc. Generally, 30 to 500 ppm of metal atoms based on the polyester produced is preferred. However, in the case of Zr compounds, it is 30 to 2500 ppm.
is preferred. In addition, in the case of Na compounds and K compounds, when added in the range of 3 to 50 ppm as metal atoms to the resulting polyester, the formation of internal particles is extremely small, and the addition of these compounds improves electrostatic adhesion. In addition, since the amount of DEG produced is reduced, when producing a polyester with high transparency, it is preferable to use a Na compound or a K compound within the above range. The formation of internal particles also changes depending on the type of P compound, and when you want to lower the internal particle concentration and obtain a polyester with high transparency, it is best to use phosphoric acid, phosphorous acid, and their esters; It is preferable to use phosphonic acid and its ester when it is desired to impart easy lifting and slipping properties. Particularly when implementing the internal particle method, the control width of precipitated particles can be improved by using a compound selected from phosphoric acid, phosphorous acid, and their esters together with a compound selected from phosphonic acids and phosphonic acid esters. This is a particularly preferred embodiment because it improves the performance.
When two or more types of P compounds are used together in this way, there is no particular limitation on the method of dividing the P compounds, and the mixed P compounds may be divided and added, or each P compound may be divided and added separately. May be added. The timing of addition of the metal compound is not particularly limited, but in the case of direct esterification, it is particularly preferable to add it when the esterification rate is 20 to 80%, since this improves the filterability of the oligomer. however,
When imparting electrostatic adhesion using a Ca compound, the effect of improving electrostatic adhesion is greater if it is added after the transesterification reaction or esterification reaction has substantially completed, so It is preferable to add. Although the additive may be added in either solid or liquid form, it is most preferable to add it as an ethylene glycol solution from the viewpoint of feeding accuracy. If it is added in solid form, it is preferably sealed in a polyester container and added to the reaction system. The timing of addition of the additive is not particularly limited as long as the above requirements are met, but it is preferable to add the additive at least before the initial condensation reaction is completed. At the end of the initial condensation reaction, the intrinsic viscosity is approximately 0.2.
After this point, the viscosity of the reaction system becomes too high and the added components become unevenly mixed, making it impossible to obtain a homogeneous product. Moreover, depolymerization of oligomers occurs, which is undesirable because it causes a decrease in productivity and an increase in the amount of DEG by-products. The present invention can be applied to both the transesterification method and the direct polymerization method. When carrying out the transesterification method, there are no particular limitations on the transesterification catalyst, and any conventionally known catalyst can be used. For example, in the additive
Ca, Mg, Li, Mn, and Zn compounds may be used, or Co compounds and the like may be used. When using the metal compound in the additive, a part of the total amount added may also be used as a transesterification catalyst, and the remaining amount may be added after the transesterification reaction is completed. Moreover, two or more types of these transesterification catalysts may be used in combination. When carrying out the direct polymerization method, there are no restrictions on the use of amines, quaternary ammonium salts, etc. as DEG generation inhibitors. Although the polycondensation catalyst is not particularly limited, it is preferable to use an appropriate selection from among Sb compounds, Ge compounds, and Ti compounds. The present invention can be applied to any of batch, semi-continuous and continuous processes. In the present invention, a lubricant made of inorganic or organic fine particles may be added to carry out transesterification, esterification, and polycondensation reactions. The polyester obtained in the present invention is suitable for use in film applications, but is not limited thereto, and can also be usefully used in fiber applications, plastic applications, etc. Next, Examples and Comparative Examples of the present invention will be shown. All parts in the examples mean parts by weight unless otherwise specified. The measurement method used is shown below. (1) Esterification rate Calculated from the amount of carboxyl groups remaining in the reaction product and the saponification value of the reaction product. (2) Intrinsic viscosity Dissolve the polymer in a mixed solvent of phenol (6 parts by weight) and tetrachloroethane (4 parts by weight) and measure at 30°C. (3) Melting specific resistance of polymer Place two electrode plates in polyester melted at 275℃, apply a voltage of 120V, measure the current value (ι ₀ ), and calculate the specific resistance value (ρι) as follows: Obtained by the formula. ρι (Ω・cm)=A/l×V/ι ₀ A=electrode area (cm ² ), l=interelectrode distance (cm)
V = Voltage (V) (4) Electrostatic adhesion A tungsten wire electrode is installed between the extruder nozzle and the cooling drum, and a voltage of 10 to 15 KV is applied between the electrode and the casting drum to cast. Staining is performed, and the surface of the resulting casting original fabric is observed with the naked eye, and evaluation is made at the casting speed at which pinner bubbles begin to occur. The higher the casting speed of the polymer, the better the electrostatic adhesion. (5) Film haze Measure with a direct reading haze meter (manufactured by Toyo Seiki Co., Ltd.). (6) Heat resistance of polymer The polymer is sealed in a glass ampoule under a nitrogen vacuum of 100 mmHg, and the change in intrinsic viscosity is measured when heated at 300°C for 4 hours. Heat resistance is expressed as the decrease in intrinsic viscosity (△IV) due to heat treatment.
The smaller ΔIV is, the better the heat resistance is. Example 1 A first esterification reactor equipped with a stirrer, a partial condenser, a raw material inlet, and a product outlet. A three-stage complete mixing tank type continuous esterification reactor was used, which consisted of a second esterification reactor equipped with a vessel, a raw material inlet, and a product outlet. A TPA/EG slurry adjusted to a molar ratio of EG to TPA of 1.7 was continuously supplied to the system containing the esterification reaction product in the first esterification reactor. At the same time, an EG solution of magnesium acetate tetrahydrate, an EG solution of sodium acetate, and an EG solution containing trimethyl phosphate and dimethyl phosphonate dissolved in a molar ratio of 1:2 are supplied from a supply port different from the TPA EG slurry supply port. and as Mg atoms, Na atoms, and P atoms, respectively, per polyester unit in the reaction product passing through the reaction vessel.
They were continuously supplied at concentrations of 100 ppm, 100 ppm, and 27 ppm, and the reaction was carried out at normal pressure for an average residence time of 4.5 hours and at a temperature of 255°C. This reaction product was continuously taken out of the system, supplied to the first tank of the second esterification reactor, and continuously taken out from the second tank. An overflow method was used for transfer from the first tank to the second tank. 0.9 parts by weight of EG and Sb per polyester unit in the reaction product passing through the reaction vessel.
In the first tank, an EG solution of antimony trioxide in an amount of 250 ppm as atoms was added as P atoms.
An EG solution containing 116 ppm of trimethyl phosphate and dimethyl phosphonate dissolved in a molar ratio of 1:2 was continuously supplied to the second tank, and the average residence time in each tank was measured at normal pressure. 2.5 hours,
The reaction was carried out at a temperature of 260°C. The esterification rate of the reaction product in the first esterification reactor was 70%, and the esterification rate of the reaction product in the second esterification reactor was 98%. The esterification reaction product is continuously filtered through a stainless wire mesh filter with an opening of 400 mesh, and then a two-stage continuous polycondensation reaction is carried out, which is equipped with a stirring device, a partial condenser, a raw material inlet, and a product outlet. Polycondensation was performed by continuously supplying the material to an apparatus to obtain a polyester having an intrinsic viscosity of 0.620. The quality of this polymer and the melt extrusion of the polymer at 290°C,
Table 1 shows the film haze of a 12μ film obtained by stretching 3.5 times in the longitudinal direction at 90°C and 3.5 times in the transverse direction at 130°C, and then heat-treating it at 220°C. As is clear from Table 1, the polyester obtained in this example has high electrostatic adhesion, excellent heat resistance, and is of extremely good quality. Comparative Examples 1 and 2 In the method of Example 1, trimethyl phosphate and dimethyl phenyl phosphonate were
Polymer obtained in the same manner as in Example 1 except that the addition of the EG solution was changed to add the entire amount at once to the second tank of the first esterification reaction tank and the second esterification reaction tank. The quality and film haze are shown in Table 1. The method of this comparative example has inferior electrostatic adhesion compared to Example 1. Comparative Example 3 In the method of Example 1, trimethyl phosphate and dimethyl phenyl phosphonate were
The addition of the EG solution was changed to adding the entire amount at once to the second tank of the second esterification reactor, and the amount added was reduced so that the metal/P ratio remaining in the polyester was 2.1. Table 1 shows the quality of the polymer and the haze of the film obtained in the same manner as in the example except for the following. It can be seen that the method of this comparative example has good electrostatic adhesion but poor heat resistance. Example 2 In the method of Example 1, the amount of sodium acetate added was reduced to 10 ppm based on the polyester produced, the P compound was reduced to only trimethyl phosphate, and the
Changed the method to add trimethyl phosphate in separate tanks, and also changed the amount of trimethyl phosphate added to each tank.
Table 1 shows the quality of the polymer and the haze of the film obtained in the same manner as in Example 1 except that the amounts were changed to 25 ppm and 80 ppm. It can be seen that the polyester obtained in this example is of high quality. Comparative Examples 4 and 5 The method of Example 2 was changed so that the entire amount of the EG solution of trimethyl phosphate was added all at once to the first tank of the second esterification reaction vessel, and the EG solution of trimethyl phosphate was
The quality of the polymer obtained in the same manner as in Example 2, except that the entire amount of the EG solution was added at once to the second tank of the second esterification reactor, and the amount added was reduced to 84 ppm. Table 1 shows the haze of the film. When the metal/P ratio was kept the same, the electrostatic adhesion was inferior to the case where the P compound of Example 2 was added separately, and when the metal/P ratio was increased, the electrostatic adhesion was made to the same level as Example 2. It can be seen that the heat resistance of the polyester is worse than in Example 2, and that the effect of adding the P compound in portions is significant. Examples 3 to 8 and Comparative Examples 6 to 11 Lithium acetate,
potassium acetate, manganese acetate, calcium acetate,
Table 1 shows the results when zinc acetate and zirconyl acetate were used. As is clear from Table 1, in both systems, the effect of adding the P compound in portions is significant. Example 9 and Comparative Examples 12 and 13 Table 1 shows the results when using the same method as in Example 1, using only magnesium acetate as the metal compound and adding it to the first tank of the second esterification reactor. . As is clear from Table 1, it can be seen that the effect of adding the P compound in portions is significant. Example 10 Using a continuous esterification reactor consisting of a two-stage complete mixing tank equipped with a stirrer, a partial condenser, a raw material inlet, and a product outlet, the esterification reaction product in the first esterification reactor was To the system where exists,
Adjust the molar ratio of EG to TPA to 1.7, and use antimony trioxide as Sb atom per TPA unit.
EG slurry of TPA containing 289 ppm was continuously fed. Average residence time 4.5 hours at normal pressure, temperature 255
The reaction was carried out at ℃. This reaction product was continuously taken out of the system and supplied to the second esterification reactor. Furthermore, 0.5 parts by weight per polyester unit was continuously added to the EG, and the average residence time was 5.0 hours at normal pressure.
The reaction was carried out at a temperature of 260°C. The esterification rate of the reaction product in the first esterification reactor is 70%, and the
The esterification rate of the reaction product in the esterification reactor is
It was 98%. 1144 parts of the esterification reaction product (equivalent to 1100 parts of ethylene terephthalate units)
and 70 parts of EG were charged into a batch type polycondensation reactor.
Heat and stir at 260°C and normal pressure for 90 minutes, then add 1.53 parts by volume of an EG solution of trimethyl phosphate at a concentration of 130 g (40 ppm in terms of P atoms based on the polyester produced) at the same temperature and pressure, and heat for 10 minutes. Stirred. Next, at the same temperature and under the same pressure, 9.34 parts by volume of an EG solution of calcium acetate monohydrate at a concentration of 50 g/min (in terms of Ca atoms based on the polyester produced) was added.
200ppm) and heated and stirred for 10 minutes, then
The concentration of
10ppm), heated and stirred for 15 minutes, and then
3.06 parts by volume of an EG solution of trimethyl phosphate (80 ppm in terms of P atoms based on the polyester produced) was added and the mixture was heated and stirred for 15 minutes. about
After gradually lowering the pressure of the reaction system to 0.5 mmHg while raising the reaction temperature to 290°C over 100 minutes,
A polycondensation reaction was carried out at 290°C and 0.5 mmHg for about 100 minutes to obtain a polymer with an intrinsic viscosity of 0.620. Table 2 shows the quality of this polymer and the film haze of the film obtained by forming the polymer by the method shown in Example 1. As is clear from Table 2, the polyester obtained in this example has high electrostatic adhesion, excellent heat resistance, and is of extremely good quality. Comparative Examples 14 and 15 In the method of Example 10, trimethyl phosphate was added during the first and second addition, respectively.
Table 2 shows the quality of the polymer and the haze of the film obtained in the same manner as in Example 10, except that the entire amount was added at once during the second addition. The methods of these comparative examples have inferior electrostatic adhesion compared to Example 10. Comparative Example 16 In the method of Example 10, the entire amount of trimethyl phosphate was added at once during the first addition, and the amount added was calculated in terms of P atoms.
Table 2 shows the quality of the polymer and the haze of the film obtained in the same manner as in Example 10 except that the concentration was changed to 96 ppm. The method of this comparative example has inferior heat resistance compared to Example 10. Example 11 1000 parts of dimethyl terephthalate in a polymerization reactor,
800 parts of EG and 0.31 part of manganese acetate tetrahydrate (70 ppm added in terms of Mn atoms to the produced polyester) were charged, and the mixture was heated at 195° C. for about 4 hours in a nitrogen atmosphere to carry out a transesterification reaction. As the transesterification progresses, the reaction temperature is increased to reach a final temperature of 240
The temperature was raised to ℃. At the same temperature, antimony trioxide was added to the transesterification product at a concentration of 12 g/ml.
31.67 parts by volume of an EG solution, 32.55 parts by volume of an EG solution of 0.1 mol% zirconyl acetate (300 ppm added in terms of Zr atoms to the polyester produced), and 12.23 parts by volume of an EG solution of magnesium acetate tetrahydrate at a concentration of 50 g In terms of Mg atoms for polyester
Add 70 ppm) and heat and stir at the same temperature and normal pressure for 15 minutes, then add 2.07 parts by volume of an EG solution of trimethyl phosphate at a concentration of 130 g/(60 ppm in terms of P atoms based on the produced polyester) and 50 g/
0.49 parts by volume of an EG solution of sodium acetate with a concentration of (7 ppm in terms of Na atoms based on the polyester produced)
was added, heated and stirred at the same temperature and normal pressure for 15 minutes, and then 5.31 parts by volume of an EG solution of trimethyl phosphate at a concentration of 130 g (154 ppm based on the polyester produced) was added and stirred at the same temperature and normal pressure for 15 minutes. After heating and stirring for a minute, the pressure of the reaction system was lowered to 0.05 mmHg while raising the temperature to 275° C. over 40 minutes, and polycondensation was carried out for about 80 minutes to obtain a polymer with an intrinsic viscosity of 0.620. Table 3 shows the quality of this polymer and the film haze of the film obtained by forming the polymer by the method shown in Example 1. It can be seen that the polyester obtained in this example has high electrostatic adhesion and is of high quality. Comparative Example 17 The quality and film quality of the polymer obtained in the same manner as in Example 11 except that the addition of trimethyl phosphate was changed to adding the entire amount at once during the first addition. The haze is shown in Table 3. The method of this comparative example has inferior electrostatic adhesion compared to Example 11. Comparative Example 18 In Example 1, the first esterification reactor and the second
The same procedure as in Example 1 was carried out except that the amount of P compound added to the second tank of the esterification reactor was reversed. Comparative Example 19 The same procedure as in Example 1 was carried out except that in Example 2, sodium dihydrogen phosphate was used instead of trimethyl phosphate in the first tank of the second esterification reactor.

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[Table] * Calculated based on the amount remaining in the polyester

[Table] * Calculated based on the amount remaining in the polyester

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Claims (1)

[Claims] 1. When producing a polyester from a dicarboxylic acid containing terephthalic acid as a main component or its ester-forming derivative and a glycol containing ethylene glycol as a main component in the presence of Ca and/or Mg compounds, metal A method for producing polyester, characterized in that a P compound that does not contain atoms is divided into two or more portions, and the amount added at the first time is less than 50 mol% of the total amount of P compound added. 2. The method for producing polyester according to claim 1, characterized in that at least one compound selected from Li, Na, K, Mn, Zn and Zr compounds is used in combination.