JP7409091B2 - Manufacturing method of polyester resin - Google Patents

Description

The present invention relates to a method for producing polyester resin.

Polybutylene terephthalate resin, which is a typical engineering plastic among thermoplastic polyester resins, is easy to mold and has excellent mechanical properties, heat resistance, chemical resistance, and other physical and chemical properties. It is widely used in automobile parts, electrical/electronic parts, precision machine parts, etc.

Polybutylene terephthalate copolymer, which has polybutylene terephthalate as a hard segment and polyol as a soft segment, is a new elastomer that can replace conventional natural rubber and synthetic rubber. It is widely used as a flexible and elastic material because it can be formed economically and has many features such as excellent rubber elasticity, heat resistance, and chemical resistance.

When using polyester resin for molded products, the color tone and heat resistance of the polyester resin affect moldability and the appearance, quality, and performance of the product. The presence of foreign matter in the polyester resin significantly impairs the appearance of the molded product, causes defects in the strength of the molded product, and causes deterioration over time.

In the production of polyester resins, direct polymerization is a useful method because it yields polymers with stable quality. It is well known that in this production method, an organic titanium compound is used as a reaction catalyst. However, organic titanium compounds tend to absorb moisture, and therefore, there is a problem in that the organic titanium compounds cause hydrolysis and significantly reduce the catalytic activity. Further, when an organic titanium compound is prepared as a catalyst, it may become insolubilized and become cloudy depending on the preparation conditions, which may clog the preparation line and deteriorate the preparation accuracy. Further, if foreign matter that has become insolubilized and becomes cloudy is supplied into the reaction system, it becomes a foreign matter in the polymer or causes an increase in haze (an indicator indicating the turbidity of a molten polymer). As a result, physical properties such as a decrease in tensile strength at break when formed into a molded product and an increase in surface foreign matter when formed into a film are caused.

In Patent Document 1, the diol compound content in the organic titanium compound added to the esterification reaction tank is 5% by weight or less, and for example, the organic titanium compound containing a small amount of diol is added to the rectification column attached to the esterification reaction tank. A method of continuous addition into the diol which is refluxed from the bottom is described.

Patent Document 2 describes a method of heating and dissolving a hindered phenol compound in a solution of an organic titanium compound prepared with 1,4-butanediol for the purpose of stabilizing a catalyst solution containing an organic titanium compound. There is.

Patent Document 3 proposes a method in which a catalyst solution prepared by adjusting 2-hydroxymethylpyridine with a diol is heated to 150°C and an organic titanium compound is added in order to obtain a polyester resin with excellent color tone and less foreign matter. .

Patent Document 4 proposes setting the pH of a titanium compound catalyst solution to 3.5 or less or 10.5 or more in order to obtain a catalyst solution for producing polyester resin that has excellent long-term storage stability.

In Patent Document 5, when a raw material slurry consisting of a dicarboxylic acid and a diol is supplied to a reaction tank, the length of the nozzle inserted into the reaction tank is changed according to the liquid level height of the reaction tank, and the line of the slurry to be supplied is changed. A polyester with excellent quality and less foreign matter has been proposed by preventing the slurry from coming into contact with the inner wall of the reaction tank by specifying the speed.

Japanese Patent Application Publication No. 2010-83948 Japanese Patent Application Publication No. 3-153731 Japanese Patent Application Publication No. 2013-136730 Japanese Patent Application Publication No. 2012-255144 Japanese Patent Application Publication No. 2013-213194

However, the method described in Patent Document 1 does not take into account deactivation measures during measurement of the organic titanium compound and adjustment with a diol, and therefore there is a problem that the organic titanium compound becomes insolubilized.

In the catalyst prepared by the method described in Patent Document 2, the hindered phenol compound itself decomposes and generates foreign substances when it is heated and dissolved and stored. In addition, when weighing the organic titanium compound into a catalyst mixing tank used in a batch-type reactor before heating and dissolving the organic titanium compound and adjusting it, the organic titanium compound, which has a high viscosity and a fast reaction rate with water, It adheres to the inner wall of the catalyst mixing tank, reacts with moisture in the atmosphere, and gradually becomes insolubilized, becoming a cloudy foreign substance. If this foreign matter falls into the reaction system, there is a problem that it increases the clogging of filters in the process, causing equipment trouble and quality trouble, and increases the amount of foreign matter in the polymer.

In Patent Document 3, pyridine is added as a third component, which may itself become a foreign substance or change the color tone of the polymer. In addition, when preparing the catalyst solution, when weighing an organic titanium compound that has a high viscosity and an extremely high reaction rate with water, the organic titanium compound adheres to the inner wall of the catalyst solution adjustment tank, and water in the atmosphere There is a problem that the organic titanium compound becomes insolubilized by gradually reacting with the organic titanium compound, producing cloudy foreign matter, but there is no disclosure of a method for reducing this foreign matter.

In Patent Document 4, since a strong acid such as hydrochloric acid is added to adjust the pH, the obtained polymer has a problem in color tone. Also, similar to Patent Documents 1, 2, and 3, when preparing the catalyst solution, no consideration is given to preventing highly active titanium compounds from adhering to the inner wall and turning into foreign matter during measurement. Therefore, there was a problem that the organic titanium compound became insolubilized.

Although Patent Document 5 mentions the suppression of foreign matter generated during supply of slurry, it does not disclose the generation of foreign matter during measurement when an organic titanium compound is used or the effect of reducing foreign matter in the obtained polyester resin. .

When a catalyst solution containing an organic titanium compound used for productivity, reaction efficiency, and quality stability is metered into a reaction tank or catalyst mixing tank , the catalyst solution containing an organic titanium compound adheres to the inner wall of the tank. It reacts with moisture in the atmosphere, becomes insolubilized, and becomes cloudy. When this happens repeatedly, the insolubilized organic titanium compound gradually accumulates on the inner wall of the reaction tank or the catalyst mixing tank, becomes a foreign substance, and deactivates the catalytic effect of the organic titanium compound, resulting in a significant decrease in productivity.

The purpose of the present invention is not only to prevent foreign matter generated when metering a catalyst solution containing an organic titanium compound to a reaction tank or catalyst mixing tank , but also to reduce the amount of foreign matter in the polymer and improve mechanical strength. The purpose of the present invention is to provide a high-quality polyester resin that has excellent color tone and can be suitably used for molded products, films, monofilaments, fibers, etc.

As a result of intensive studies to achieve the above object, the present inventors found that when a catalyst solution containing an organic titanium compound used in producing polyester resin is metered and added, the organic titanium compound becomes insolubilized and becomes cloudy. The present invention was achieved by discovering a method for producing a polyester resin that does not cause any problems and has few foreign substances.

That is, the present invention
When manufacturing a polyester resin by subjecting a dicarboxylic acid or its ester-forming derivative to a diol or its ester-forming derivative through an esterification reaction or transesterification reaction, and a polycondensation reaction, the esterification reaction, transesterification reaction, and polycondensation reaction are performed. During at least one reaction selected from condensation reactions, a catalyst solution containing an organic titanium compound is supplied to one selected from an esterification reaction tank, a transesterification reaction tank, and a polycondensation reaction tank using an internal nozzle. is added to the reaction tank, and the internal nozzle has a cut surface of the nozzle tip that is horizontal in a plane projected from the side of the nozzle tip, and an angle between the cut surface of the nozzle tip and the upper surface of the nozzle ( This method of producing polyester resin is characterized in that the nozzle tip angle) is 40° to 50°.
Moreover, the present invention
Organic titanium A method for producing a polyester resin, in which a catalyst solution containing a compound is metered into a catalyst mixing tank using an internal nozzle, the internal nozzle is configured to add a catalyst solution containing a compound to a catalyst mixing tank using an internal nozzle. This method of producing a polyester resin is characterized in that the cut surface is horizontal and the angle between the cut surface of the nozzle tip and the upper surface of the nozzle (nozzle tip angle) is 40° to 50°.

According to the present invention, when metering a catalyst solution containing an organic titanium compound into any reaction tank or catalyst mixing tank selected from an esterification reaction tank, a transesterification reaction tank, and a polycondensation reaction tank , It can be produced using a highly active catalyst without the titanium compound becoming cloudy due to deactivation or insolubilization, prevents the generation of foreign matter, has a small amount of foreign matter, and has excellent mechanical strength and color tone. It is possible to provide a highly productive polyester resin that can be suitably used for molded products, films, monofilaments, fibers, etc.

FIG. 1 is a schematic diagram illustrating a polyester resin production facility. FIG. 2 is an example of a side projection view of the nozzle tip used for adding a catalyst solution containing an organic titanium compound in the present invention. FIG. 3 is another example of a side projection view of the nozzle tip used for adding a catalyst solution containing an organic titanium compound in the present invention.

The present invention solves the above-mentioned problems, that is, prevents the generation of foreign matter, and has made extensive studies on a method for producing polyester resin that has a small amount of foreign matter in the polymer and is highly productive. When metering a catalyst solution containing an organic titanium compound into a reaction tank during at least one reaction selected from It has been determined that the problem can be solved all at once.

The polyester resin of the present invention is obtained by subjecting a dicarboxylic acid or an ester-forming derivative thereof to a diol or an ester-forming derivative thereof to an esterification reaction or transesterification reaction in a batchwise or continuous manner, followed by a polycondensation reaction. , is a polyester resin.

The polyester resin produced in the present invention is preferably a polybutylene terephthalate polymer using terephthalic acid as the dicarboxylic acid and 1,4-butanediol as the diol, and other acid components and/or other diol components. Polybutylene terephthalate copolymers used as copolymerization components are also preferred. In this case, examples of acidic components include aromatic dicarboxylic acids such as isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, and sodium sulfoisophthalic acid; alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid and decalindicarboxylic acid; Examples include aliphatic dicarboxylic acids such as malonic acid, succinic acid, sebacic acid, adipic acid, and dodecanedioic acid. Tricarboxylic acids such as trimellitic acid may also be used. Examples of diol components include aliphatic diols such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, neopentyl glycol, 1,6-hexanediol, polypropylene glycol, and polytetramethylene glycol; Examples include alicyclic diols such as cyclohexane diol and 1,4-cyclohexanedimethanol, and aromatic diols such as 2,2-bis(4'-hydroxyphenyl)propane. Each of these copolymerized components is preferably present in an amount of 40 mol % or less relative to terephthalic acid or 1,4-butanediol. Also preferred is a polyester elastomer resin using a polyol as the diol.

In a preferred embodiment of the present invention, the molar ratio of the diol component to the dicarboxylic acid component is preferably 1.0 to 1.5, more preferably 1.1 to 1.3.

In the present invention, a catalyst solution containing a necessary organic titanium compound is added to the reaction tank during at least one reaction selected from esterification, transesterification, and polycondensation. The organic titanium compound acts as a catalyst during the esterification reaction, transesterification reaction, and polycondensation reaction.

Specifically, the organic titanium compound used in the present invention includes titanic acid methyl ester, tetra-n-propyl ester, tetraisopropyl ester, tetra-n-butyl ester, tetraisobutyl ester, tetra-tert-butyl ester, tetra- Examples include -2 ethylhexyl ester, tetraoctyl ester, phenyl ester, benzyl ester, tolyl ester, and mixed esters thereof. Among these, tetra-n-propyl ester (tetra-n-propyl titanate), tetraisopropyl ester (tetra-isopropyl titanate), and tetra-n-butyl ester (tetrabutoxytitanate) of titanic acid are preferred because they can be obtained at low cost. Tetra-n-butyl ester of titanic acid (tetrabutoxytitanate) is particularly preferably used. These organic titanium compounds may be used alone or in combination of two or more. Further, the amount of the organic titanium compound in the catalyst solution containing the organic titanium compound (hereinafter sometimes referred to as an organic titanium compound catalyst solution) is preferably 10 to 30% by weight, more preferably 15 to 25% by weight. In the present invention, tetrabutoxy titanate is preferably used from the viewpoint of reactivity.

As the solvent for the organic titanium compound catalyst solution, organic solvents such as ethylene glycol and 1,4-butanediol are preferable, and among these, 1,4-butanediol is preferable.

In the organic titanium compound catalyst solution, a known organic tin compound catalyst such as monobutyltin oxide or dibutyltin oxide can be used in combination, if necessary.

Further, in the present invention, esterification or transesterification reaction and polycondensation reaction of terephthalic acid or dimethyl terephthalate with 1,4-butanediol etc. are carried out, but these reaction conditions are not particularly limited. , well-known reaction conditions for polyester production can be used as they are. Furthermore, various additives such as matting agents, optical brighteners, stabilizers, ultraviolet absorbers, flame retardants, antistatic agents, crystal nucleating agents, etc. can also be used as appropriate.

In the method for producing a polyester resin of the present invention, when metering and adding the organic titanium compound catalyst solution to the reaction tank, it is necessary to add the organic titanium compound catalyst solution without contacting the inner wall surface of the reaction tank. .

Further, the reaction tank may be any of an esterification reaction tank that performs an esterification reaction, a transesterification reaction tank that performs a transesterification reaction, and a polycondensation reaction tank that performs a polycondensation reaction .

The present invention will be explained in detail below using a case in which a catalyst mixture is prepared by adding a catalyst solution containing an organic titanium compound to a catalyst mixing tank by metering, but the present invention is not limited thereto. do not have.

The usual method of metering and adding a catalyst solution containing an organic titanium compound to a region other than the gas phase in a catalyst mixing tank is to directly add it to the liquid phase (catalyst mixture) from the middle to lower part of the catalyst mixing tank. ing. These methods have the problem that the organotitanium compound metered and added tends to solidify and the vicinity of the metering and addition port for the catalyst solution containing the organic titanium compound tends to be clogged, and it has not been possible to deal with this problem satisfactorily.

On the other hand, even when a catalyst solution containing an organic titanium compound is supplied to the gas phase of a catalyst mixing tank, if the catalyst solution is supplied while being in contact with the inner wall of the catalyst mixing tank so that it flows down, the organic titanium compound will Titanium derived from the organotitanium compound component in the catalyst solution containing the catalyst may become insolubilized and solid matter may be generated. If this solid substance mixes with the catalyst mixture in the catalyst mixing tank and is discharged from the esterification reaction tank without being sufficiently dispersed or reacted in the subsequent esterification reaction tank, it will clog the oligomer filter in the transfer pipe and stop the operation. It may cause trouble. Furthermore, if the product passes through the filter or if no filter is provided in the piping, there is a risk that solid matter may be mixed into the product.

Because of these problems, it is practically undesirable to meter and add a catalyst solution containing an organic titanium compound by flowing it down (while making contact with) the inner wall of the catalyst mixing tank.

In the method for producing a polyester resin of the present invention, in order to supply a catalyst solution containing an organic titanium compound to the gas phase part in the catalyst mixing tank, for example, a catalyst solution addition port containing an organic titanium compound is provided in the upper part of the catalyst mixing tank. It is preferable to use a method in which a catalyst solution containing an organic titanium compound is supplied thereto through a connecting pipe for the catalyst solution containing an organic titanium compound.

In order to supply the catalyst solution containing the organic titanium compound into the catalyst mixing tank without contacting the inner wall surface of the catalyst mixing tank, an internal nozzle connected to the piping and inserted into the catalyst mixing tank may be used. is preferred. By supplying the catalyst solution containing the organic titanium compound through such an internal nozzle, it is possible to prevent the catalyst solution containing the organic titanium compound from coming into contact with the inner wall surface or dripping.

An internal nozzle is used when metering the catalyst solution containing the organotitanium compound into the catalyst mixing tank. In the internal nozzle, the cut surface of the nozzle tip needs to be horizontal, that is, parallel to the liquid level of the catalyst mixing tank, in a plane projected from the side of the nozzle tip. Furthermore, it is necessary to use an internal nozzle in which the angle between the cut surface of the nozzle tip and the upper surface of the nozzle (nozzle tip angle) is 40° to 50° in the plane projected from the side of the nozzle tip. . When the nozzle tip angle is smaller than 40°, the area of the cut surface of the nozzle tip becomes large, and the jetting angle of the catalyst solution containing the organic titanium compound becomes large.The catalyst solution containing the organic titanium compound is sprayed onto the inner wall of the catalyst mixing tank, and Organic titanium compounds accumulate on the inner wall of the mixing tank and become foreign matter. If the nozzle tip angle is larger than 50°, repeated metered additions of a catalyst solution containing an organic titanium compound will cause the organic titanium compound to accumulate at the nozzle tip, clogging the nozzle tip, and the deposited organic titanium compound will turn into foreign matter. Therefore, it is not desirable. Although FIGS. 2 and 3 show examples of side projection views of the nozzle tip used for adding the catalyst solution containing the organic titanium compound in the present invention, the present invention is not limited thereto.

By using an internal nozzle with such a shape, it is possible to easily add the catalyst solution containing the organic titanium compound to the catalyst mixture from the gas phase without contacting the inner wall surface of the catalyst mixing tank. This is preferable because it can be done.

In addition, in the method for producing polyester of the present invention, the linear velocity when metering the catalyst solution containing the organic titanium compound into the catalyst mixing tank (volume flow rate of the catalyst solution containing the organic titanium compound to be metered/containing the organic titanium compound) The cross-sectional area of the end opening on the catalyst mixing tank side of the catalyst solution metering addition line is usually 0.01 m/sec or more, preferably 0.03 m/sec, more preferably 0.05 m/sec. That's all. The upper limit is usually 0.09 m/sec or less, preferably 0.07 m/sec or less.

Further, in the present invention, when metering the catalyst solution containing the organic titanium compound into the catalyst mixing tank, it is preferable to purge the catalyst mixing tank with nitrogen. If purging is not performed, the highly active organic titanium compound reacts with moisture in the atmosphere and becomes insolubilized, which is not preferable.

As described above, the catalyst solution containing the organic titanium compound may be diluted with 1,4-butanediol in the catalyst mixing tank and added to the esterification reaction tank as a catalyst mixture. The pH of 1,4-butanediol used in the catalyst mixing tank is preferably 6.5 to 7.5. A pH of 6.5 to 7.5 is preferable because hydrolysis of the organic titanium compound with water is suppressed. Although the mechanism for the pH of 1,4-butanediol is not clear, it is presumed that it changes depending on the difference in the content of a trace amount of catalyst due to differences in manufacturing methods. Further, a diol having such a pH can be preferably used as a raw material for polyester resin.

Although there is no particular restriction on the basic method for producing the polyester resin of the present invention, the esterification reaction tank is preferably a complete mixing tank type esterification reaction tank. The esterification reaction is preferably carried out at a reaction temperature of 180° C. to 250° C., more preferably 200° C. to 240° C., and under a reduced pressure of preferably 760 mmHg or less, more preferably 100 to 700 mmHg.

Furthermore, in order to obtain a polyester resin with excellent crystallinity, it is preferable to carry out the esterification reaction at a reaction temperature of 200° C. to 240° C. and a pressure of 100 mmHg to 700 mmHg. Further, the reaction rate of the polyester oligomer after the total esterification reaction is preferably 97% or more, more preferably 99% or more. The polyester oligomer produced by the esterification reaction is then subjected to a polycondensation reaction, but the method is not particularly limited, and the polymerization conditions used for the production of ordinary polyester resins can be directly adopted. For example, the reaction temperature is preferably 230°C to 260°C, more preferably 240°C to 250°C.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples, but the present invention is not limited thereto. In addition, the method for producing polyester resin by measuring the addition of a catalyst solution containing an organic titanium compound in Examples 1 to 6 and Comparative Examples 1 to 3 was performed up to 50 times (50 batches), and evaluated as follows. The results of Examples 1 to 6 and Comparative Examples 1 to 3 are summarized in Table 1.

(1) Presence or absence of metering nozzle:
The presence or absence of a metering nozzle is shown when metering and adding a catalyst solution containing an organic titanium compound to a catalyst mixing tank.

(2) Tip angle of metering nozzle:
The angle of the tip of the metering nozzle (1) above is shown in FIG.

(3) Measuring nozzle clogging tendency number of batches (batches):
Based on the time required for charging the first batch of organic titanium compound into the catalyst mixing tank, the number of batches was measured when the required time exceeded three times.

(4) Number of batches where metering nozzle clogs occur (batches):
The number of batches was measured at the time when the nozzle for metering and adding the catalyst solution containing the organic titanium compound became clogged and metering could no longer be added.

(5) Filter replacement frequency:
Based on the time required for transferring the liquid from the esterification reaction tank to the polycondensation reaction tank for the first batch of the test, if the required time exceeded 5 minutes from the reference time, it was determined that the filter was clogged and the filter was replaced. The number of batches at the time when this filter exchange was performed was measured.

(6) Foreign matter content:
A total of 100 g of the pelletized polymer was taken out from the inside, and foreign matter contained in the chips with a size of 1 mm ² or more was counted.

[Example 1]
Figure 1 shows an outline of the device. 250 parts by mass of 1,4-butanediol with a pH of 7.2 heated at 100°C was charged into a catalyst mixing tank 3 equipped with a stirrer 2, and while stirring the inside of the catalyst mixing tank 3 at 30 rpm, the organic titanium compound was measured. 4.7 parts by weight of a catalyst solution containing an organic titanium compound was metered and added from nozzle 1 at a linear velocity of 0.05 m/sec while purging the catalyst mixing tank with nitrogen to obtain a catalyst mixture used for the esterification reaction. In this case, the angle 7 of the tip of the organic titanium compound metering nozzle was 45°.

Next, 1,4-butanediol having a pH of 7.2 was charged in an esterification reaction tank 5 equipped with a stirrer 6 at a ratio of 789 parts by weight to 1561 parts by weight of terephthalic acid, and mixed in the catalyst mixing tank described above. The entire amount of the prepared catalyst mixture is charged from the charging line 4 to the esterification reaction tank 5, and the temperature is gradually raised in a controlled range from 190°C to 240°C while stirring, and the water produced is distilled off to form an esterification reaction product. I got it.

Next, 55 parts by mass of 1,4-butanediol with a pH of 7.2 heated at 100° C. was charged into a catalyst mixing tank 3 equipped with a stirrer 2, and while stirring the inside of the catalyst mixing tank 3 at 30 rpm, organic titanium was added. 5.2 parts by weight of a catalyst solution containing an organic titanium compound was metered and added from the compound metering nozzle 1 at a linear velocity of 0.05 m/sec while purging the catalyst mixing tank with nitrogen to obtain a catalyst mixture used for the polycondensation reaction. Ta.

Next, the catalyst mixture used for the polycondensation reaction was added to the esterification reaction product from the catalyst mixing tank 3 via the charging line 4, and the mixture was stirred and mixed with the esterification reaction product for 5 minutes to obtain an esterification reaction solution.

Note that the amount of the organic titanium compound in the catalyst solution containing the organic titanium compound added to the catalyst mixing tank from the organic titanium compound metering nozzle 1 is 20% by weight.

Next, the esterification reaction liquid is transferred from the esterification reaction tank 9 to a polycondensation reaction tank equipped with a stirrer, which is connected via a liquid transfer line equipped with a 40 μm filter, via a liquid transfer line equipped with a filter. It liquefied.

Next, the esterification reaction solution in the polycondensation reaction tank was heated at 250° C. under reduced pressure (1 mmHg or less), and the polycondensation reaction was terminated when a specified stirring torque was reached. The time required to reach the specified stirring torque at 250° C. under reduced pressure (1 mmHg or less) is defined as the polycondensation reaction time. After that, the polycondensation reaction tank was pressurized to 0.30 MPa with nitrogen, and the polymer was discharged in the form of a strand through a nozzle (not shown), solidified with cooling water, and pelletized with a cutter (not shown). did.

When the above method was repeated to polymerize the polyester resin, the organic titanium compound nozzle did not tend to clog, and continuous operation of 50 batches was possible. The filter installed in the liquid transfer line for the esterification reaction product was replaced every 40 batches.

[Example 2]
Example 1 was carried out in the same manner as in Example 1 except that the angle of the nozzle tip of the organic titanium compound metered into the catalyst mixing tank was set to 50°. As a result, the filter was replaced in 37 batches, and the system could be operated for a sufficiently long time.

[Example 3, 4]
Example 1 was carried out in the same manner as in Example 1, except that the amount of the organic titanium compound in the organic titanium compound catalyst solution measured into the catalyst mixing tank was changed. As a result, we were able to operate for a sufficiently long time without having to replace the filter.

[Example 5]
Example 1 was carried out in the same manner as in Example 1 except that the pH of the 1,4-butanediol used was changed to 6.5. As a result, the filter was replaced in 40 batches. Although the polycondensation reaction time was longer, it was within a usable range.

[Example 6]
Example 1 was carried out in the same manner as in Example 1 except that 170 parts by weight of polytetramethylene glycol (PTMG) as a copolymerization component was added to the polycondensation reaction tank. As a result, the filter was replaced in 40 batches, and the system could be operated for a sufficiently long time.

[Comparative example 1]
Example 1 was carried out in the same manner as in Example 1, except that the nozzle for metering the organic titanium compound into the catalyst mixing tank was removed. As a result, the number of filter replacements was shortened to five batches, the polycondensation reaction time became longer, and the content of foreign substances increased. It can be seen that the effects of the present invention cannot be obtained without a nozzle for metering the organic titanium compound.

[Comparative Examples 2 and 3]
Example 1 was carried out in the same manner as in Example 1 except that the angle of the nozzle tip of the organic titanium compound metered into the catalyst mixing tank was changed. As a result, the number of filter replacements was as short as 10 batches, the polycondensation reaction time was long, and the content of foreign substances was high. It can be seen that the effects of the present invention cannot be obtained when the nozzle tip angle for metering the organic titanium compound is outside the range of 45° to 50°.

1 Organotitanium compound catalyst solution metering addition nozzle (internal nozzle)
2 Stirrer 3 Catalyst mixing tank 4 Preparation line 5 Esterification reaction tank 6 Stirrer 7 Nozzle tip angle

Claims (6)

When manufacturing a polyester resin by subjecting a dicarboxylic acid or its ester-forming derivative to a diol or its ester-forming derivative through an esterification reaction or transesterification reaction, and a polycondensation reaction, the esterification reaction, transesterification reaction, and polycondensation reaction are performed. During at least one reaction selected from condensation reactions, a catalyst solution containing an organic titanium compound is supplied to one selected from an esterification reaction tank, a transesterification reaction tank, and a polycondensation reaction tank using an internal nozzle. A method for producing a polyester resin added to a reaction tank, wherein the internal nozzle has a cut surface of the nozzle tip that is horizontal in a plane projected from the side of the nozzle tip, and a cut surface of the nozzle tip and the nozzle. A method for producing a polyester resin, characterized in that the angle formed by the nozzle with the upper surface (nozzle tip angle) is 40° to 50°. Organic titanium A method for producing a polyester resin, in which a catalyst solution containing a compound is metered into a catalyst mixing tank using an internal nozzle, the internal nozzle is configured to add a catalyst solution containing a compound to a catalyst mixing tank using an internal nozzle. A method for producing a polyester resin, characterized in that the cut surface is horizontal and the angle between the cut surface of the nozzle tip and the upper surface of the nozzle (nozzle tip angle) is 40° to 50°. The method for producing a polyester resin according to claim 1 or 2, wherein the amount of the organic titanium compound in the catalyst solution containing the organic titanium compound is 10 to 30% by weight. 4. The method for producing a polyester resin according to claim 1, wherein the organic titanium compound is tetrabutoxytitanate. 5. The method for producing a polyester resin according to claim 1, wherein the diol is 1,4-butanediol having a pH of 6.5 to 7.5. 6. The method for producing a polyester resin according to claim 1, wherein the polyester resin is one selected from a polybutylene terephthalate polymer and a polybutylene terephthalate copolymer.

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