JPS6160722A - Production of polyester - Google Patents

Abstract

PURPOSE:To obtain a polyester which can give a film improved in abrasion resistance and slidability, by adding a specified particulate substance to the reaction system before starting the polycondensation reaction and precipitating specified particles during the polycondensation reaction in producing a polyester. CONSTITUTION:In producing a polyester by transesterifying or esterifying terephthalic acid or its esterifiable derivative with a gycol and subsequently performing a polycondesation reaction, a particulate substance being insoluble in the system and having a specific surface area >=5m<2>/g is dispersed in the system with the aid of 0.5-50wt%, based on the substance, organic basic com pound at an arbitrary point before starting the polycondensation, and further particles having at least one of an alkali metal and an alkaline earth metal as part of constituents are precipitated during the polycondensation reaction. As said particulate substance, silicon dioxide, calcium carbonate or the like can be desirably used. Examples of the organic basic compounds used in the dispersion treatment include tetramethyl-ammonium hydroxide and diethano lamine.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a polyester m-sheet, a polyester film,
Alternatively, the present invention relates to a method for producing polyester molded articles having improved runnability, abrasion resistance, and surface properties.

[Prior art and its problems] Polyester in general, and polyethylene terephthalate in particular, has excellent mechanical properties, heat resistance, weather resistance, electrical insulation, and chemical resistance, so it is used not only as textiles for clothing and industrial purposes, but also as films for magnetic tapes and photographs. It is widely used in the film field such as electric insulation film, capacitor film, etc.

When polyester is used in the film field, it is necessary to ensure process passability through the forming processes of melt extrusion, stretching, and heat treatment, or during film forming, winding, cutting, surface coating of magnetic layers, etc., and incorporation into electrical parts. We produce polyvarnish and chill compositions containing microparticles from the viewpoint of final product value such as durability, film product tear resistance, abrasion resistance, and surface properties. , If! It is common practice to facilitate film flow during fi11 and to improve surface properties and abrasion resistance.

Examples of polyester compositions containing such fine particles include: polyester compositions obtained by adding and blending inert, insoluble fine particles such as dihydric oxide, titanium dioxide, calcium carbonate, talc, clay, and organic polymers; ■ Polyester compositions obtained by precipitating fine particles containing alkali, alkaline earth, and other metal compounds added to the polyester synthesis system as well as phosphorus compounds during the polycondensation reaction process, etc. It has been known.

However, such known fine particle-containing polyester compositions have the following problems, and especially when formed into a film, their slipperiness, abrasion resistance, surface condition, film formability, etc. are not satisfactory. There wasn't.

That is, in a polyester composition that has been subjected to C10 by the method of adding insoluble fine particles described in (1) above, it is difficult to make the added particles fine and coarse particles are mixed together due to the agglomeration of particles, resulting in a non-uniform particle system. .

In addition, coarse protrusions caused by coarse particles coexist, causing problems such as fish eyes and dropouts.Furthermore, in order to prevent fine particles from agglomerating together, dispersants that are added often interfere with the heat resistance and electrical properties of these polyesters. This results in disadvantages such as deterioration of characteristics. Therefore, JP-A-53-1
In order to finely disperse the particles, Japanese Patent No. 25495 discloses an example in which the added particles are finely dispersed using a special stirring blade to be present in the polyester, but the purpose has not been fully achieved.・On the other hand, when polyester compositions containing particles obtained by the so-called fine particle precipitation method described in (1) above, it is difficult to control the particle size of the precipitated particles when the particle content is increased, and furthermore, in order to increase the particle amount, it is difficult to control the particle size of the precipitated particles. If the addition amount is increased, problems such as an increase in coarse particles due to agglomeration of particles will occur. For example, JP-A-53-4103 discloses an example of precipitated particles containing lithium element, but it has not yet shown sufficient effects in the above-mentioned applications.

Particularly in recent years, the use of magnetic tapes has grown significantly, and magnetic tapes have come to be used in many applications such as audio tapes, video tapes, and memory tapes, and the required properties are becoming increasingly sophisticated.

(2) It is necessary to reduce the thickness of the magnetic tape in order to make it smaller and increase the height to 195 degrees, and there is an increasing demand for making the irregularities on the film surface more uniform and fine.

Furthermore, a polyester film is obtained by blending with a polyester that does not contain particles or contains few particles, and good surface properties are imparted to the polyester film.
In order to produce molded products with excellent slipperiness, raw materials are required that are free of coarse particles and contain a large amount of fine particles. However, the finer these particles are and the larger the amount of particles, the more likely coarse particles are to be produced due to aggregation of particles.

[Object of the invention] The present inventors have developed the previous 3c! In view of the actual situation, we investigated a manufacturing method for polyester that has a large amount of uniform fine particles and is effective in improving the abrasion resistance and slipperiness of the film when it is formed into a film, and the present invention was completed.

[Structure of the invention]

The purpose of the present invention described above is to carry out the transesterification or esterification reaction between terephthalic acid or its ester-forming derivative and glycol, and then to carry out the polycondensation reaction to produce a polyester. At this point, the specific surface area insoluble in the system was 5 m 2 /g.
The above particulate matter 111vJ is applied to the particulate matter from 0.5 to
It is characterized in that it is added after dispersion treatment using 50% by weight of an organic basic compound, and further, during the melon condensation reaction, particles containing one or more types of alkali gold Ii1 or alkaline earth metals as part of the constituent components are precipitated. This can be achieved by a polyester manufacturing method.

The polyester referred to in the present invention is mainly composed of polyethylene terephthalate that can be molded into fibers, films, and other molded products, and even if it is a homopolyester,
Examples of components that can be copolymerized even if they are copolyesters include diol components such as diethylene glycol, propylene glycol, neopentyl glycol, polyalkylene glycol, P-xylylene glycol, P-cyclohexane dimetatool, and 5-sodium sulforesorcin. , dicarboxylic brewing ingredients such as adipic acid, sebacic acid, phthalic acid, isophthalic acid, 2,6-naphthalene dicarboxylic acid, and 5-sodium sulfoisophthalic acid, polyfunctional dicarboxylic brewing ingredients such as trimellitic acid and pyromellitic acid, P -oxyethoxycarboxylic acid components. When the dicarboxylic acid is a dicarboxylic acid, the dicarboxylic acid is subjected to an esterification reaction with a glycol, and when a dicarboxylic acid ester is used, the resulting prepolymer is subjected to a polycondensation reaction under reduced pressure to form a polyester. do.

Depending on the type of particulate matter insoluble in the reaction system used in the present invention, the alkali gold l1Ir precipitated during the polycondensation reaction
3 and/or alkaline earth metals and phosphorus compounds as groove components, it affects the particle size. Silicon dioxide, calcium carbonate, magnesium carbonate, aluminum silicate, talc, and silicon dioxide, calcium carbonate, magnesium carbonate, aluminum silicate, talc, and Inorganic particles such as titanium, mica, calcium phosphate, barium sulfate and '+1! Examples include crosslinkable resin powder such as paddle polyester, and organic fine particle powder such as Teflon powder.

Further, among the above particulate materials, silicon dioxide, calcium carbonate, aluminum silicate particles, etc. can be preferably used.

The specific surface area of the particulate matter insoluble in the reaction system by the BET method is 5 T11'/Il+ or more, but preferably 30
vn'/0 or more and 1000 m''/9 or less, particularly preferably 80 is 7 g or more and 800 Tl'/il+.

If the specific surface area of the particulate matter that is insoluble in the reaction system is less than 5/2, the particle size of the precipitated particles will be different from that of the precipitated particles, and it will be difficult to produce uniform fine particles. become unable. In addition, when using inert 4-particles, 1 is 0.005 to 2.01 with respect to the total acid component constituting the polyester.
11 m% is preferable, J: 117 tl, or 0.01
It is in the range of ~1.0ff11%.

The organic basic compounds used in the dispersion treatment of the particulate matter include quaternary ammonium compounds such as tetramethylammonium hydroxide, tetraethylammonium hydroxide, and tetramethylammonium halides, ethanolamine,
jetanolamine, di-n-butylamine, di-n-
Examples include amines such as butylamine, di-n-propylamine, diphenylamine, and naphthylamine, and ammonia.

Yes) The amount of IH base compound used is 0.5 to 50% of the particulate matter! I! It needs to be in the range of 5% to 30%, preferably 5% to 30%! Eiff1%, particularly preferably 10~
The range is 30111%.

If it is less than 0.51%, a sufficient dispersion effect on particulate matter cannot be obtained, and if it is more than 501%, no further effect can be obtained.

The dispersion treatment of the particulate material with an organic base compound is preferably carried out in a medium, and in view of the reaction after being added to the reaction system, it is preferable to carry out the dispersion treatment in ethylene glycol and prepare an ethylene glycol slurry. The ethylene glycol slurry can be prepared by a conventionally known preparation method, such as finely dispersing the slurry using a special mixing device disclosed in JP-A-53-125495. In this case, particulate matter ethylene, glycol slurry and
Separately prepare ethylene glycol solution of organic base compound wA
After the preparation, the particulate matter is mixed and dispersed, and the particulate matter is added to the ethylene glycol solution of the organic base compound and finely dispersed. It is necessary to carry out a dispersion treatment before adding the compounds into the polyester polycondensation system by any method, such as adding the compounds at the same time and finely dispersing them.

The ethylene glycol slurry of the particulate material dispersed using the above-mentioned in base compound may be added to the reaction system at any time before the start of the m-condensation reaction.

Alkali metal for producing precipitated particles used in the present invention,
Examples of the alkaline earth metal scrap compounds include alkali metals, alkaline earth metal hydrides, alcolades, chlorides, hydroxides, carbonates, carboxylates, sulfates, and the like.

Specific examples include lithium acetate, lithium chloride, sodium acetate, lithium hydroxide, calcium acetate, and magnesium chloride. Among them, hydroxides of calcium and lithium, and aliphatic carbon 1illlu generate a large amount of precipitated particles, suppress side reactions, and W! It is preferably used because of ease of processing. The amount of these metal compounds used is preferably 0.00 based on the total acid components constituting the polyester.
5 to 3% by weight, more preferably 0.01 to 2% by weight,
11a It is added at any time before the start of the synthesis reaction, particularly preferably after the transesterification or esterification reaction is substantially completed and before the start of the polycondensation reaction.

Further, in the present invention, it is desirable to use a phosphorus compound to generate precipitated particles. As the phosphorus compound, one or more selected from the group consisting of phosphoric acid, phosphorous acid, or their methyl esters, ethyl esters, phenyl esters, their halfesters, phosphonic acids, phosphinic acids, or their esters. can be mentioned. The amount of the phosphorus compound to be used depends on the metal compound used, but it is preferably 0.001 to 2% by weight, more preferably 0.01 to 21% by weight, based on the total acid components constituting the polyester. It is. The timing of addition is preferably after the completion of esterification or transesterification,
m is added at any time before the start of the condensation reaction.

Further, in the present invention, the quantitative ratio between particulate matter insoluble in the reaction system and precipitated particles precipitated in the reaction system is preferably such that the ratio of precipitated particles to particulate matter is 0.1 to 50 in terms of weight.
More preferably 0°3 to 30, even more preferably 0.5
~10.

The precipitated particles were measured using the following method.

(Method for determining precipitated particles) Approximately 300 g of a polymer composition or film was taken, 2.7 g of 0-chlorophenol was added to it, and the temperature was raised to 100° C. with stirring. Let it stand for a while to dissolve the polymer part.

However, if the polymer portion is not sufficiently dissolved under these conditions, such as when it is highly crystallized, the polymer composition can be melted and then rapidly cooled as a sample, and the melting process can be carried out under the above-mentioned melting conditions. Then ultracentrifuge 1400 for min #1
Rotor Rp method to rotor Rp method (Hitachi vJ)
After injecting 3 Qcc of the above solution per cell, the rotor was rotated at 450 Orpm, and after confirming that there was no abnormal rotation, the inside of the rotor was evacuated and the particles were centrifuged.

Separation was completed after approximately 40 minutes, but confirmation of this took place within minutes.
This is done by ensuring that the light transmittance at 375 millimicrons of the liquid after separation becomes a constant value that is higher than that before separation.

Separate particles are obtained by removing the supernatant liquid by decanting. Since the fraction 111 particles may be contaminated with polymer parts due to insufficient separation, O-chlorophenol at room temperature is added to the collected particles to homogeneously suspend them, and then the centrifuge treatment is performed again.

This operation, which will be described later, must be repeated until a melting peak corresponding to the polymer can no longer be detected by scanning differential calorimetry analysis of the particle portion after drying the particles. Finally, the separated particles thus obtained were vacuum dried at 120°C for 16 hours and weighed, and the amount of particulate matter added to the polyester reaction system was subtracted from Bfl to determine the amount of precipitated particles. .

In addition, in the present invention, in the esterification reaction or Nisdell exchange reaction, alkali metals such as lithium, sodium, and potassium, alkaline earth metals such as magnesium, calcium, strontium, and barium, and hydrides of zinc and manganese are used as catalysts. , alcoholades, chlorides and glycol-soluble salts of monocarboxylic acids are preferably used as catalysts. Particularly preferred is acetic acid.
These include calcium acetate, strontium acetate, zinc acetate, manganese acetate, and manganese chloride.

In addition, typical catalysts used for the polycondensation of bishydrooxyalkyl esters of aromatic dicarboxylic acids are glycol-soluble antimony or germanium compounds.
Specifically, antimony trioxide, antimony potassium tartrate,
Antimony oxychloride, germanium oxide, and the like are preferably used.

[Effect of the invention 1] The polyester of the present invention contains a large amount of uniform and fine precipitated particles, and is characterized in that it contains extremely few coarse particles compared to polyester obtained by conventional precipitated particle generation methods or addition methods.

Furthermore, the particles of the present invention have good compatibility with polyester, and when producing 41 fibers or films from the polyester, the following effects, which could not be achieved with conventional particles, are exhibited.

(2) There is less clogging of the filter during the melt-molding process into fiber N and film, and a film with good workability in the post-processing process can be obtained.

■ Even if MtA is formed into a very thin film with a thickness of 3 microns or less, it contains many particles consisting of uniformly fine precipitated particles and particulate matter that is insoluble in the reaction system, so there may be problems between the films or between the films. There is no blocking phenomenon between the gold side L film and the felt, and a polyester film is obtained which has excellent slipperiness, has good surface properties, and has excellent abrasion resistance with little grain drop-off.

■ In addition, since it contains a large number of uniform fine particles, it can be used diluted, and in this case too, there is no film fisheye, and especially in magnetic tape applications, there is no dropout, image unevenness, or sound skipping during playback. Useful.

The polyester obtained by the present invention can be preferably used not only for m-fibers such as multifilaments and stable, unoriented, -axially oriented, and biaxially oriented films, but also for e-nofilaments and plastics.

The present invention will be explained in detail with reference to Examples below.

Incidentally, each characteristic value of the obtained polyester was measured according to the following method.

(A) Particle Size Rank of Particles in Polymer Polymer 20+a9 was placed between 2'J and two-piece cover glasses, melt-pressed at 280°C, subjected to cold NI, subjected to microscopic vAH, and ranked based on the average particle diameter as follows. A: Particle size less than 1.0 microns B: Particle size 1.0 microns or more and less than 3 microns C: Particle size 3
Micron or more and less than 5 micron D: Particle size of 5 micron or more (B) Particle dispersion of particles in polymer Polymer 20io is sandwiched between two cover glasses 28
After melt pressing at 0°C and cold FA, microscopic observation was performed and 1ffi
The following judgment is made based on the number of coarse particles of 3 microns or more present in I12.

Grade 1: 10g/IIIg of coarse particles exceeding 3 microns
Less than 2 exist.

2nd grade = 10 to 30 coarse particles exceeding 3 microns/
mm2 exists.

Grade 3: 30 coarse particles exceeding 3 microns/III
Exists beyond I12.

(C) Intrinsic viscosity of polymer This is a value measured at 25°C using O-chlorophenol as a solvent.

(D>Film properties a) 1f cooling coefficient of film Measured using a slip tester according to ASTM-D-1894B method. Incidentally, the static emissivity coefficient was used as a measure of the film's easily erasable properties.

b) Roughness of film surface irregularities The film surface was observed using a stylus type roughness meter, and the difference between the highest and lowest parts of the Iζ surface irregularities was expressed in microns.

Example 1 Calcium acetate 0.09 parts by weight from 100 parts by weight of dimethyl terephthalate and 70 parts by weight of ethylene glycol
A transesterification reaction was carried out by a conventional method using Shabu as a catalyst, and the product contained 0.0310 parts of andemon trioxide,
0.3 mi parts of lithium acetate, 0.21 parts of trimethyl phosphate
m parts and previously added 10 parts of well-finely dispersed silicon dioxide (specific surface area 200/(1>0.2110 Then, polymerization was carried out in a conventional manner to obtain a polymer having an intrinsic viscosity of 0.614.The dispersibility of the particles in the polymer was first class, and the particle size was palanque, which was extremely good.

Comparative Example 1 After completing the transesterification reaction in Example 1, 0.31 d part of lithium acetate and 0.2 part of trimethyl phosphate were added to the product.
ff! A polymer having an intrinsic viscosity of 0.609 was obtained in the same manner as in Example 1, except that only part ffi and 0.03 part i part of antimony trioxide were added and reacted. The dispersibility of the particles in the polymer was 3rd grade, and the particle size was C rank, which was not preferable.

Examples 2 to 5 if 5 and comparative implementation @ 2.3 A polyester composition was prepared using the same method as in Example 1, such as the amount of inert particles added and the source of precipitated particles, except that the type of inert particles was changed and the reaction was carried out. Table 1 shows the types of added particles, the particle size and dispersibility of the particles in the polymer.

Table 1 (blank space below) Comparative Example 4 A transesterification reaction was carried out from 1 part of dimethyl terephthalate and 70 fltff of ethylene glycol by a conventional method using 0.09 part of calcium as a catalyst.
The product contains anti-1 trioxide: 0,03 fn
Quantity PJs, yeast Fli! J thium 0, 3 fil
m parts, 0.2 fffli parts of trimedel phosphate were added,
Polymerization was performed using the 1:r method to reach the target viscosity and torque. Next, the pressure was returned to normal pressure, and 10mfn% was added in advance.
Well-finely dispersed silicon dioxide (specific surface Tj'1200m"10
) 0.2 parts of fflffi was added, and while the pressure was gradually reduced, ethylene glycol was removed by distillation, and silicon dioxide was dispersed and mixed into the polymer to finally obtain a polymer with an intrinsic viscosity of 0.602. The particle size in the polymer had a double distribution of A and C ranks, and the dispersibility was also 3rd grade, which was not preferable.

Example 6 The transesterification reaction was completed using J3 in Example 1, and the product was mixed with 0.06 mff1 part of lithium acetate and 1 liter of submersible.
10.03 overlap and 20fflf for particles in advance
10 using fi% tetraethylammonium hydroxide
Well-finely dispersed silicon dioxide (specific surface area 250tn'/IJ
) A polymer having an intrinsic viscosity of 0.621 was obtained in the same manner as in Example 1, except that 0.05 part by weight was added and the reaction was carried out. The particle size in the polymer was Parank, and the particle dispersibility was 1 Wi, which was extremely preferable.

Comparative Example 5 The esterification reaction product was charged into an esterification reaction vessel equipped with a stirrer, a partial condenser, and a raw material inlet, and dissolved by heating at 250° C. in the presence of nitrogen gas. An ethylene glycol slurry of terephthalic acid with a molar ratio of ethylene glycol to terephthalic acid adjusted to 1.20 was continuously supplied to the reaction vessel, water was distilled off, and an esterification reaction was carried out. 105 parts by weight of the esterified product (equivalent to 100 flffi parts of ethylene terephthalate units) was charged into a condensation reactor and maintained at 250°C, and 0.02 parts by weight of trimethyl phosphate and 0.025 fn of antimony trioxide were added.
ffi part, 0.2 part by weight of silicon dioxide (specific surface area 200 x/Ω), which has been finely dispersed in advance as an ethylene glycol slurry with a concentration of 1% by weight using 10% tetraethylammonium hydroxide based on the particles. was added and the pressure inside the system was gradually reduced to carry out a polycondensation reaction to obtain a polymer with an intrinsic viscosity of 0.611.

The polymer 50 (iffi part and the polymer 50ffJffi part Iq in Comparative Example 1) were melted and kneaded at a temperature of 285°C for 10 minutes to obtain 1q of polymer having an intrinsic viscosity of 0.590.The particle size rank in the polymer was It showed a wide distribution of A to C, and the dispersibility was also tertiary, which was not preferable.

Example 7 The polyester composition obtained in Example 1 was treated with 29
Formed into a sheet at 0°C and stretched at a longitudinal stretching ratio of 3.
After stretching at a transverse stretching ratio of 3 times and 3.4 times, heat treatment was performed at 215° C. to obtain a film having a thickness of 12 μm. Work stability during film formation was good, and there were no problems such as film breakage. The friction coefficient of the rolled film is 0.67, and the average roughness of the film surface is 0.028 microns.

The maximum film surface roughness was 0.28, which was good.

Comparative Example 6 A film with a thickness of 12 microns was prepared in the same manner as in Example 7 except that a polyester composition of Comparative Example 1 was used. The average roughness of the surface of the obtained film was 01039.
The maximum roughness of the film surface was 0.41 microns, which was not favorable in terms of surface properties of the film 11.

Example 8 Dimethyl terephthalate 100f[! Manganese acetate 0.03 from fd part and 70ffilB part of ethylene glycol
A transesterification reaction is carried out by a conventional method using 11 parts of 5r as a catalyst, and the product contains 0.03f of antimony trioxide.
A nfti product, Trimethyl Phosphate 03025, was added and polymerized by a conventional method to obtain a polymer having a limiting viscosity of 0.620. The polyfluoride 5jlt part and the polymer 2 obtained in Example 1
After U-combining at a mixing ratio of 5 parts by weight, a film with a thickness of 12 microns was obtained in the same manner as in Example 7. film j
i! Friction coefficient 0.90, average roughness of film surface 0.01
8 microns, and the maximum film surface roughness was 0.19 microns [1 nm], which was good.

Example 9 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 151 parts of calcium acetate as a catalyst were charged into a transesterification reaction 8ffi equipped with a stirrer, a partial condenser, and a raw v1 charging port, and heated and stirred. did. 10f for the particles in advance while stirring the solution.
1 using f11% tetraethylammonium hydroxide
0.01% ethylene glycol slurry (finely dispersed silicon dioxide (specific surface area 200 m'/(1)0.01%).
2ffl& parts were added, and the transesterification reaction was carried out in a conventional manner, and the resulting product contained 0.21n parts of lithium acetate, 0.21 parts of trimethyl phosphate, and 0 parts of antimony trioxide.
．． 03W was added, and the pressure was gradually reduced to carry out the I7 condensation reaction. Finally 0, 7a+m1-IQ, 2
The reaction was carried out at 90°C for about 4 hours. The intrinsic viscosity of the polymer 1q was 0.622, the particle size in the polymer was Parank, and the particle dispersibility was first grade, which was good.

Example 10 The esterification reaction product was charged into an esterification reaction vessel equipped with a stirrer, a partial condenser, and a raw material inlet, and dissolved by heating at 250° C. in the presence of nitrogen gas.

Ethylene glycol for terephthalic acid: 1-
An ethylene glycol slurry of terephthalic acid with a molar ratio of 1.20 to 1 was continuously supplied to distill off water to carry out an esterification reaction.

105 parts by weight of the esterified raw acid (equivalent to 10,011 parts of ethylene terephthalate units) was charged into the old condensation reactor, maintained at 250'C, and 0.05 parts by weight of calcium Mate.
Rain a part, lithium acetate 0.20ffll 11 parts, +J>
FIJ +); 0.15 m parts of ethyl, 0.03111 parts of antimony trioxide, 10 ftlf using 20% tetraethylammonium hydroxide based on the particles in advance
Well-finely dispersed silicon dioxide (specific surface area 200 m'/g>0
．． After adding 21 parts by weight, the pressure inside the system was gradually reduced to carry out a condensation reaction. @Hiragi 0.7aa+Hf1l, 2
The reaction was carried out at 90°C for about 4 hours. The obtained polymer had an intrinsic viscosity of 0.616, a particle size in the polymer of Palanc, and a first grade particle dispersibility, which was good.

Example 11 In Example 1, the transesterification reaction was completed, and the product was mixed with 0.3l1fff1% of lithium acetate, and 1% of lithium acetate was added to the product. ! 1
0.15! 11 parts Hf and 211% pre-particles
10 using ammonia! Well-finely dispersed silicon dioxide (specific surface area: 250 x/g) was added as 11% vague ethylene glycol slurry by adding 0.2 parts of heavy stone.
A polymer with an n-limiting viscosity of 0.613 was obtained. The particle size rank in the polymer was A1, and the particle dispersibility was 1st grade, which was extremely preferable.

Claims (1)

[Claims] When producing a polyester by transesterifying or esterifying terephthalic acid or its ester-forming derivative with a glycol and subsequently carrying out a polycondensation reaction, at any point before the start of the polycondensation reaction, insoluble A particulate material having a specific surface area of 5 m^2/g or more is added by dispersion treatment using an organic base compound of 0.5 to 50% by weight based on the particulate material, and an alkali metal or alkali is further added during the polycondensation reaction. A method for producing polyester, which comprises precipitating particles having one or more earth metals as part of their constituent components.