JP3357489B2 - Polyester production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyester, and more particularly, to a polyester which has a small amount of acetaldehyde and hardly increases acetaldehyde even during molding, and can simplify the production process. And a method for producing such a polyester.

[0002]

BACKGROUND OF THE INVENTION Bottles obtained by biaxially stretching a saturated polyester such as polyethylene terephthalate are excellent in transparency, mechanical strength, heat resistance and gas barrier properties, and are used in juices, soft drinks, carbonated drinks and the like. Are widely used as beverage filling containers (PET bottles).

In order to produce a bottle from such a polyester, for example, it is usual to produce a preform by injection molding the polyester and then to biaxially stretch the preform into a bottle shape by blow molding or the like. It is manufactured by.

[0004] If acetaldehyde remains in the bottle obtained from the polyester as described above, the taste of the contents to be filled is significantly reduced. For this reason, it is desirable that the acetaldehyde content contained in the polyester forming the bottle is as low as possible. In order to reduce the amount of acetaldehyde contained in the polyester forming the bottle, it is necessary to use a polyester that has a small amount of acetaldehyde before molding and that does not easily increase the amount of acetaldehyde even during bottle molding.

By the way, polyester is obtained by subjecting a dicarboxylic acid such as terephthalic acid or an ester derivative thereof to a diol or an ester derivative thereof such as ethylene glycol, and then subjecting the esterified product to a polycondensation reaction in the presence of a polycondensation catalyst. It is manufactured by doing. This polycondensation reaction is performed in a liquid-phase polycondensation step and a solid-phase polycondensation step, and the polyester obtained in the liquid-phase polycondensation step is then subjected to solid-phase polycondensation to obtain a high intrinsic viscosity and acetaldehyde. A polyester having a reduced content is obtained.

As described above, in the method for producing polyester,
A liquid-phase polycondensation step and a solid-phase polycondensation step must be performed. However, this solid-phase polycondensation requires a long time, resulting in an increase in production cost.

If the polyester obtained by liquid-phase polycondensation is to be directly produced into a molded article such as a bottle without omitting the solid-phase polycondensation step, acetaldehyde is generated during molding, and this acetaldehyde is contained in the polyester molded article. There is a problem that it remains.

[0008] Therefore, it is possible to provide a polyester having a very small amount of acetaldehyde and also having a small amount of acetaldehyde during molding of a bottle or the like.
In addition, there is a demand for a polyester production method that can omit the solid-phase polycondensation step.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and has as its object to provide a polyester which has a small amount of acetaldehyde and hardly increases acetaldehyde during molding of a bottle or the like. It is an object of the present invention to provide a method for producing a polyester which can be performed and can omit the solid-phase polycondensation step.

[0010]

SUMMARY OF THE INVENTION The process for producing a polyester according to the present invention comprises: [A] heating a dicarboxylic acid containing terephthalic acid or its ester derivative and a diol containing ethylene glycol or its ester derivative in the presence of a polycondensation catalyst. A liquid phase polycondensation step of melting and liquid phase polycondensation to produce a polyester (a) having an intrinsic viscosity of 0.7 to 1.5 dl / g measured in o-chlorophenol; [C] The polyester (a) obtained in the liquid phase polycondensation step [A]
[D-1] The polyester (c) that has been subjected to the hot water treatment step of contacting with hot water of 0 to 130 ° C. for 5 minutes to 10 hours and the hot water treatment step described above is heated at 110 to 150 ° C. for 30 minutes. ~
A drying step of drying for 6 hours and [D-2] the polyester (c) which has been subjected to the above drying step is heated to a temperature of 160 to 200 ° C. for 1 hour.
A heating step of heating for 10 to 10 hours, wherein the polyester (d) obtained has an acetaldehyde content of 10 ppm or less.

In the method for producing a polyester according to the present invention, the polyester (a) obtained in the liquid phase polycondensation step [A] is used.
After a preliminary crystallization step in which [B] an elevated temperature crystallization temperature (Tc ₁ ) to 200 ° C. is maintained for 1 minute to 4 hours,
[C] It may be supplied to the hot water treatment step.

In the above production method, the polyester obtained in the step [A] preferably has an intrinsic viscosity of 0.8 to 1.2 dl / g measured in o-chlorophenol.

According to the production method of the present invention, it is possible to omit the solid-phase polycondensation step in producing polyester, to produce a polyester having a small amount of acetaldehyde and hardly increasing acetaldehyde during molding. it can. The polyester obtained in the present invention is suitable as a material for forming a preform and a beverage bottle.

[0014]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, a method for producing a polyester according to the present invention will be specifically described with reference to a process flow shown in FIG. As shown in FIG. 1, the manufacturing method according to the present invention comprises:

[A] A dicarboxylic acid containing terephthalic acid or an ester derivative thereof and a diol containing ethylene glycol or an ester derivative thereof are heated and melted in the presence of a polycondensation catalyst to undergo liquid phase polycondensation. 0.7-1.5 dl / g intrinsic viscosity measured in chlorophenol
A liquid phase polycondensation step of producing a polyester (a),
[C] a hot water treatment step of bringing the polyester (a) into contact with hot water at 60 to 130 ° C. for 5 minutes to 10 hours;
[D-1] Polyester (c) having undergone the above hot water treatment step
Is dried at a temperature of 110 to 150 ° C. for 5 minutes to 6 hours, and [D-2] the polyester (c) that has been subjected to the above hot water treatment step is heated to a temperature of 160 to 200 ° C. for 1 to 10 hours. Heating step of heating, the resulting polyester (d)
Has an acetaldehyde content of 10 ppm or less.

In the present invention, the polyester (a) obtained in the liquid-phase polycondensation step [A] is treated with [B] a heated crystallization temperature (Tc).
₁ ) After passing through a preliminary crystallization step of maintaining the atmosphere at a temperature of 200 ° C. for 1 minute to 4 hours, it may be supplied to the [C] hot water treatment step. Hereinafter, each step will be described in detail.

[A] Liquid phase polycondensation step In the present invention, first, in the [A] liquid phase polycondensation step, dicarboxylic acid containing terephthalic acid or an ester derivative thereof (for example, lower alkyl ester, phenyl ester, etc.) and ethylene glycol Is heated and melted in the presence of a polycondensation catalyst to form a liquid phase polycondensation with a diol or an ester derivative thereof (eg, a monocarboxylic acid ester) to produce a polyester (a).

In the present invention, homopolyethylene terephthalate may be produced using terephthalic acid and ethylene glycol, or a dicarboxylic acid containing not more than 20 mol% of a dicarboxylic acid other than terephthalic acid in addition to terephthalic acid. The copolymerized polyester can also be produced using a diol containing 20 mol% or less of a diol other than ethylene glycol in addition to ethylene glycol.

The dicarboxylic acids other than terephthalic acid used in producing the copolyester include phthalic acid (orthophthalic acid), isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid and the like. An aromatic dicarboxylic acid,
Examples thereof include aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelaic acid, and decanedicarboxylic acid, alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid, and ester derivatives thereof. These may be used in combination of two or more.

Examples of the diol other than ethylene glycol include dimethylene glycol, trimethylene glycol (propylene glycol), tetramethylene glycol, neopentyl glycol, hexamethylene glycol, dodecamethylene glycol, diethylene glycol, and triethylene glycol. , Aliphatic glycols such as tetraethylene glycol and polyethylene glycol, alicyclic glycols such as cyclohexanedimethanol, aromatic diols such as bisphenols, hydroquinone, and 2,2-bis (4-β-hydroxyethoxyphenyl) propane; These ester derivatives are exemplified. These may be used in combination of two or more.

In the present invention, a small amount of a structural unit derived from a polyfunctional compound such as trimesic acid, pyromellitic acid, trimethylolethane, trimethylolpropane, trimethylolmethane, and pentaerythritol, for example, 2 mol% or less. Polyester containing polyester can also be produced. The present invention can be carried out in either a batch system or a continuous system, and the continuous system will be specifically described below.

In the liquid phase polycondensation step [A], the above-mentioned dicarboxylic acid or its ester derivative (hereinafter, referred to as “the ester derivative”) is used.
Polyester is produced by polycondensation of diol or an ester derivative thereof (hereinafter sometimes also referred to simply as diol) with polycarboxylic acid).
In this liquid phase polycondensation step, first, a dicarboxylic acid and a diol are first subjected to an esterification reaction (an esterification reaction step [A-
1]), followed by a liquid phase polycondensation reaction (polycondensation reaction step [A-
2])

Specifically, first, a slurry containing a dicarboxylic acid and a diol is prepared. Such a slurry contains 1.02-2.0 moles, preferably 1.03-1.5 moles of diol per mole of dicarboxylic acid. This slurry is continuously supplied to the esterification reaction step [A-1].

In the esterification reaction, water or alcohol produced by the reaction is removed outside the system by a rectification column under the condition that the diol is refluxed, for example, using a device in which two esterification reactors are connected in series. It can be implemented while.

When the esterification reaction step [A-1] is carried out in two stages, the first stage of the esterification reaction usually has a reaction temperature of 240 to 270 ° C., preferably 245 to 265 ° C., and a pressure of 0.2 to 3 kg. / Cm ² G, preferably 0.5 to ² kg / cm ² G, and the second stage of the esterification reaction usually has a reaction temperature of 250 to 280 ° C., preferably 255 to 275 ° C., and a pressure of 0 to 1. 5 kg / cm ² G, preferably 0 to 1.3 kg / cm ² G
It is carried out under the following conditions.

Although the reaction rate of the esterification reaction in each of these stages is not particularly limited, it is preferable that the degree of the increase in the esterification reaction ratio in each stage is smoothly distributed, and the esterification reaction in the second stage is further performed. It is usually desirable for the reaction product to reach 90% or more, preferably 93% or more.

An esterified product (lower condensate) is obtained by the above esterification step [A-1], and the number average molecular weight of the lower condensate is usually from 500 to 5,000. Such an esterification reaction can be carried out without adding additives other than dicarboxylic acids and diols, and can be carried out in the presence of a polycondensation catalyst described later. Tertiary amines such as tri-n-butylamine and benzyldimethylamine, quaternary ammoniums such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, It can be carried out by adding a small amount of a basic compound such as sodium acetate. These basic compounds may be added to all of the esterification reactors, or may be added to the first or second stage specific reactor.

The esterified product thus obtained is
Subsequently, it is continuously supplied to a liquid phase polycondensation reactor. In the liquid-phase polycondensation reactor, the resulting polyester is heated to a temperature not lower than the melting point of the obtained polyester under reduced pressure in the presence of a polycondensation catalyst, and the resulting glycol is distilled out of the system and polycondensed.

In the present invention, the polycondensation reaction step [A-2] comprises:
It may be performed in one stage or may be performed in a plurality of stages.
When the polycondensation reaction step is performed in a plurality of stages, the first
The second stage polycondensation reaction is usually performed at a reaction temperature of 250 to 290 ° C.
The reaction is preferably carried out at a temperature of 260 to 280 ° C. and a pressure of 500 to 20 Torr, preferably 200 to 30 Torr. The reaction is carried out under a condition of 0.1 Torr, preferably 5 to 0.1 Torr, particularly preferably 2 to 0.1 Torr.

When the polycondensation reaction step is carried out in three or more stages, the polycondensation reaction from the second stage to the last stage before the first stage depends on the reaction conditions of the first stage and the final stage. The reaction is performed under the conditions between the reaction conditions. For example, if the polycondensation reaction step is 3
When carried out in stages, the second stage polycondensation reaction is:
Usually, the reaction temperature is 260-295 ° C, preferably 270-2 ° C.
The reaction is carried out at 85 ° C. and at a pressure of 50 to 2 Torr, preferably 40 to 5 Torr.

In the present invention, in the above-mentioned [A] liquid-phase polycondensation step, the intrinsic viscosity measured in o-chlorophenol at 25 ° C. is 0.7 to 1.5 dl / g, preferably 0.1 to 1.5 dl / g. A polyester (a) having a weight of 8 to 1.2 dl / g is produced. In addition, the intrinsic viscosity reached in each stage except the last stage of the liquid phase polycondensation reaction step is not particularly limited, but it is preferable that the degree of increase in the intrinsic viscosity in each stage is smoothly distributed.

[A] In the liquid phase polycondensation step, to produce a polyester (a) having such an intrinsic viscosity,
The above-mentioned polycondensation reaction step [A-2] is desirably carried out in three or more stages, preferably three stages, and the final stage (third stage)
The intrinsic viscosity of the polyester supplied to the polycondensation reaction of the step (d) is 0.4 to 0.7 dl / g, preferably 0.5 to 0.65.
It is desirably dl / g.

In order to obtain the polyester (a) having such an intrinsic viscosity by a multi-stage polycondensation reaction, a known liquid-phase polycondensation reactor can be used in combination. For example, in the first stage, a vertical reactor is used. In the second stage, a horizontal reactor having a single-screw agitator can be used, and in the third stage, a horizontal reactor having a twin-screw agitator can be used. In this specification, the intrinsic viscosity is obtained by adding 1.2 g of polyester to o-
After heating and dissolving in 15 ml of chlorophenol, the solution is cooled and calculated from the solution viscosity measured at 25 ° C.

The liquid phase polycondensation reaction is carried out in the presence of a catalyst. As the catalyst, germanium compounds such as germanium dioxide, germanium tetraethoxide, and germanium tetra n-butoxide, antimony catalysts such as antimony trioxide and antimony acetate, and titanium catalysts such as titanium tetrabutoxide can be used.

The use of a germanium dioxide compound among these catalysts is preferred because a polyester having excellent hue and transparency can be obtained. The polycondensation reaction is preferably performed in the presence of a stabilizer.

Examples of the stabilizer include phosphates such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate and tricresyl phosphate, triphenyl phosphite, trisdodecyl phosphite, tris Phosphites such as nonylphenyl phosphite, acid phosphates such as methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate, dioctyl phosphate, and phosphoric acid, and polyphosphoric acid. A phosphorus compound is used.

The above catalyst is used in an amount of 0.0005 to 0.2% by weight, preferably 0.001 to 0.2% by weight, based on the total weight of the dicarboxylic acid and the diol, in terms of the weight of the metal in the catalyst.
Preferably, it is used in an amount of .about.0.05% by weight.

The stabilizer is used in an amount of 0.001 to 0.1% by weight, preferably 0.002 to 0.1% by weight in terms of phosphorus atom weight in the stabilizer with respect to the total weight of dicarboxylic acid and diol.
Desirably, it is used in an amount of 0.02% by weight. These catalysts and stabilizers can be supplied in the esterification reaction step as described above, or can be supplied to the first stage reactor in the polycondensation reaction step. In this way, the polyester (a) obtained from the final liquid-phase polycondensation reactor is usually formed into granules (chips) by a melt extrusion molding method.

[B] Pre-crystallization step In the present invention, a pre-crystallization step may be added to the granular polyester (a) that has been subjected to the liquid phase polycondensation step in this way. This pre-crystallization step is carried out by keeping the granular polyester (a) in a dry state at a temperature of a temperature-increased crystallization temperature (Tc ₁ ) to 200, preferably at a temperature of Tc _{1 to} 180 ° C. for 1 minute to 4 hours. Done.

This pre-crystallization step is preferably performed in air or in an inert atmosphere. The polyester (b) after the pre-crystallization preferably has a crystallinity of 20 to 50%.

In such a pre-crystallization step, the so-called solid-state polycondensation reaction of the polyester does not proceed, and the intrinsic viscosity of the polyester (b) after the pre-crystallization is obtained in the liquid-phase polycondensation step [A]. About the same as the intrinsic viscosity of the polyester (a).

By adding a pre-crystallization step to the polyester in this way, the content of acetaldehyde contained in the polyester can be reduced, and the granular polyester (chip) is fused in the hot water treatment step or the drying step. Can be prevented.

[C] Hot Water Treatment Step In the production method according to the present invention, the polyester as described above
(a) or pre-crystallized polyester (b) is treated with hot water.

This hot water treatment is carried out in the granular polyester (a).
(Or (b)) is brought into contact with heated water, steam, steam-containing inert gas, steam-containing air, or the like. The contact between the granular polyester (a) (or (b)) and hot water is preferably carried out by mixing the polyester, usually 60-130.
C., preferably by immersion in hot water heated to a temperature of 80 to 100.degree.

This granular polyester (a) (or (b))
Contact with hot water is usually 5 minutes to 10 hours, preferably 3 minutes.
Performed for 0 minute to 5 hours. Granular polyester (a)
(Or (b)) is usually 6
The granular polyester (a) (or (b)) is supplied at a temperature of 0 to 130 ° C, preferably 80 to 100 ° C, with steam or a steam-containing inert gas or steam-containing air in an amount of 0.5 g or more per kg of the granular polyester. ) And water vapor.

The contact between the granular polyester and steam is carried out usually for 5 minutes to 10 hours, preferably for 1 hour to 8 hours. The granular polyester (c) immediately after the hot water treatment as described above usually has a water content of 5,000 to 10,000 ppm.
It is contained in the amount of.

By subjecting the polyester to the hydrothermal treatment as described above, the increase in acetaldehyde during molding can be suppressed. By performing the hydrothermal treatment on the polyester in this way, it is possible to suppress the increase of acetaldehyde contained in the polyester during molding,
By subjecting the polyester to hydrothermal treatment, the polycondensation catalyst, such as a germanium catalyst, contained in the polyester is deactivated, so that even when heated during molding, the decomposition reaction or transesterification reaction hardly progresses. It is likely that the amount of

[D-1] Low-Temperature Drying Step In the method for producing a polyester according to the present invention, the polyester (c) subjected to the hydrothermal treatment as described above is then dried at a low temperature. Specifically, polyester (c) subjected to hydrothermal treatment
Is desirably dried at a temperature of 110 to 150 ° C., preferably 120 to 140 ° C., for 30 minutes to 6 hours, preferably 1 hour to 4 hours. The polyester (c) from which moisture has been removed by low-temperature drying as described above is preferable because hydrolysis is prevented.

[D-2] Heat Treatment Step In the production method according to the present invention, the polyester (c) that has been subjected to the hot water treatment and dried at a low temperature as described above is then heated at a high temperature. Specifically, the polyester (c) is
At a temperature of 200C, preferably 170-190C, 1-1.
Heat for 0 hours, preferably 2 to 6 hours. More specifically, the polyester (c) is heated to a temperature of 160 to 200 ° C., preferably 170 to 190 ° C., in a flowing gas (air,
Nitrogen gas).

For example, when the polyester is polyethylene terephthalate, specifically, 160 to 200
The temperature may be in contact with a flowing gas heated to a temperature of preferably from 170 to 190 ° C.

By heating under such conditions,
The acetaldehyde contained in the polyester is removed, and a polyester (d) containing only a small amount of acetaldehyde is obtained. In this [D-2] heating step, the polyester polycondensation reaction hardly proceeds, and the intrinsic viscosity of the polyester (c) obtained after the heat treatment is determined by the polyester (a) obtained in the liquid phase polycondensation step.
About the same as the intrinsic viscosity.

In the method for producing a polyester according to the present invention, the [B] pre-crystallization step, [D-1] low-temperature drying step and [D-2] heating step are performed at a lower temperature than the so-called solid-state polymerization step. In addition, as described above, in the [D-1] low-temperature drying step and the [D-2] heating step, the polycondensation reaction of the polyester does not substantially proceed because the catalyst has been deactivated. The intrinsic viscosity of the polyester does not substantially increase, and a polyester having a small amount of acetaldehyde can be obtained.

The polyester produced in the present invention has (i) an acetaldehyde content of 10 ppm or less, preferably 5 ppm or less, and (ii) an intrinsic viscosity measured in o-chlorophenol of usually 0%. 0.7-1.5 dl / g, preferably 0.8-1.1 dl / g, particularly preferably 0.8-1.0 dl / g.

The polyester produced in the present invention preferably has a crystallinity of 30 to 50%. Thus, the polyester obtained by the production method according to the present invention,
Not only the acetaldehyde content is low, but also little acetaldehyde is generated during molding. In particular,
The polyester produced according to the present invention has a molding temperature of 270
Although injection molding is performed at 310 ° C., for example, 290 ° C., the molded article such as the obtained preform usually has an acetaldehyde content of 20 ppm or less, preferably 15 ppm or less.

A bottle obtained by supplying such a polyester to a molding machine such as an injection molding machine to form a preform for a hollow molded body, inserting the preform into a mold having a predetermined shape, and stretch blow molding. Hollow molded containers such as
It does not change the taste of the contents. The polyester produced in the present invention is suitably used particularly as a material for forming a beverage bottle and a preform material for forming the bottle.

[0056]

The polyester obtained by the method for producing a polyester according to the present invention not only has a low acetaldehyde content, but also has a small amount of acetaldehyde produced during molding. The container does not change the taste of the contents.

In the method for producing a polyester according to the present invention, there is no need to perform a solid-phase polycondensation step on the polyester, which is excellent in productivity and economy. Thus, the polyester obtained by the method for producing a polyester according to the present invention is suitable as a material for a preform or a beverage bottle.

[0058]

EXAMPLES Next, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

In the present specification, the acetaldehyde concentration (ppm) is measured for a stepped square plate-like molded product as shown in FIG. 2 which is injection molded from a polyester chip as follows. The stepped square plate-like molded product has a thickness of the portion A of 2 mm,
The thickness of the part B is 4 mm, the thickness of the part C is 6 mm, and the thickness of the part D is 3
mm, the thickness of the portion E is 5 mm, and the thickness of the portion F is 7 mm. Using this part E, the acetaldehyde concentration of the molded article is measured.

The dried and dried polyester chips of the stepped rectangular plate-like molded product were manufactured by Meiki Seisakusho Co., Ltd.
Dew point is -70 ° C during molding by -70A injection molding machine
Is fed to the upper portion of the hopper and the screw feeder chute at a rate of 5 Nm ³ / hour, and the barrel temperature is 290 ° C. and the temperature of the C1 / C2 / C3 / nozzle tip of the molding machine is 260 ° C./280° C./280. Injection molding was performed at a temperature of 15 ° C. at a temperature of 15 ° C. at a temperature of 300 ° C./300° C. to obtain a stepped square plate-shaped molded product as shown in FIG. Injection molding of the stepped square plate-like molded product is performed by supplying a polyester chip, which has been dried so that the measurement time is 12 seconds and the injection time is 60 seconds, from a hopper to an injection molding machine. The residence time of the molten resin in the molding machine is about 72 seconds. In addition, the weight per one stepped square plate-shaped molded product is about 75 g.

Measurement of Acetaldehyde Concentration The acetaldehyde concentration of the stepped square plate-shaped product was determined by subjecting a sample to pulverization with a freezer mill, extracting acetaldehyde in the sample with hot water, and using gas chromatography to determine the internal standard method. Quantified by

Measurement of elevated crystallization temperature A sample from the center of a polyester chip dried at about 140 ° C. under a pressure of about 5 mmHg for about 5 hours or more using a DSC-2 type differential scanning calorimeter manufactured by Perkin Elmer Co., Ltd. 10mm
g in a liquid aluminum pan under a nitrogen atmosphere. The measurement conditions were as follows: first, the temperature was rapidly raised from room temperature, melted and maintained at 290 ° C. for 10 minutes, then rapidly cooled to room temperature, and then the peak temperature of the exothermic peak detected when the temperature was raised at a rate of 10 ° C./minute Ask for.

Intrinsic Viscosity The intrinsic viscosity (dl / g) of the polyester was obtained by dissolving a sample in o-chlorophenol (OCP) by heating, measuring the solution viscosity with a capillary viscometer, and using the value and an empirical formula prepared in advance. Was.

[0064]

Example 1 100 parts by weight of terephthalic acid, 50.5 parts by weight of ethylene glycol and 0.0 of germanium dioxide
26 parts by weight were added, and an esterification reaction was carried out by a conventional method. The liquid temperature at the end of the reaction was 240 ° C. Next, 0.030 parts by weight of trimethyl phosphate was added, and a polycondensation reaction was performed in three stages. In the final stage, the reaction temperature is 270 ° C,
A polycondensation reaction is performed at a reaction pressure of 1 Torr, and an intrinsic viscosity of 0.84
dl / g of polyester was obtained. The acetaldehyde concentration of the polyester chip was 90 ppm, and the heating crystallization temperature was 164.8 ° C.

Next, the polyester chips were pre-crystallized at 170 ° C. for 2 hours under a nitrogen flow. After the pre-crystallization, the chip had an intrinsic viscosity of 0.83 dl / g and an acetaldehyde concentration of 22 ppm. Then 95
It was immersed in hot water at 4 ° C. for 4 hours, dried at 130 ° C. for 2 hours under a nitrogen stream, and then heated at 180 ° C. for 2 hours. Table 1 shows the intrinsic viscosity, acetaldehyde concentration, and water content of the polyester chip in each processing step.

[0066]

[Table 1]

Further, the polyester chip was dried at 160 ° C. for 3 hours under a nitrogen flow to reduce the water content in the chip to 20 pp.
m. At this time, the chips had an intrinsic viscosity of 0.79 dl / g and an acetaldehyde concentration of 3.6 ppm. Then, it was heated and melted at a temperature of 290 ° C. to form a stepped square plate. The molded product had an acetaldehyde concentration of 15 ppm.

The chip was molded using a molding machine M manufactured by Meiki Seisakusho Co., Ltd.
It was molded at -100A to obtain a bottle preform. At this time, the molding temperature was 270 ° C., the nozzle temperature was 310 ° C., the mold temperature was 10 ° C., and the acetaldehyde concentration in the preform was 10 ppm.

[0069]

COMPARATIVE EXAMPLE 1 The same raw material chips as in Example 1 were preliminarily crystallized at 170 ° C. for 2 hours under a nitrogen flow, and then were heated to 130 ° C.
C. for 2 hours and heated at 180.degree. C. for 2 hours.
After the treatment, the obtained polyester chips have an intrinsic viscosity of 0.8
The concentration was 0 dl / g and the concentration of acetaldehyde was 4.4 ppm.
Next, after drying at 160 ° C. for 3 hours, it was heated and melted at a temperature of 290 ° C. to form a stepped square plate. The molded product had an acetaldehyde concentration of 30 ppm. A preform was formed in the same manner as in Example 1, and the concentration of acetaldehyde in the preform was measured.

[0070]

Example 2 Using the same raw materials as in Example 1, the polyester chips were treated in the same manner as in Example 1.
Without pre-crystallization, dipped in hot water of 95 ° C for 4 hours, and then dried at 130 ° C under low-temperature for 2 hours under flowing nitrogen, then 170 ° C
For 4 hours. Table 2 shows the intrinsic viscosity of the chip, the concentration of acetaldehyde and the moisture in the chip in each step.
Shown in

[0071]

[Table 2]

After further drying at 160 ° C. for 3 hours,
It was heated and melted at 0 ° C. to form a stepped square plate. The molded product had an acetaldehyde concentration of 17 ppm. A preform was formed in the same manner as in Example 1, and the concentration of acetaldehyde in the preform was 11 ppm.

[Brief description of the drawings]

FIG. 1 is a process flow showing a method for producing a polyester according to the present invention.

FIG. 2 is a perspective view of a stepped square plate formed in the example.

Claims (8)

(57) [Claims] [A] A dicarboxylic acid containing terephthalic acid or its ester derivative and a diol containing ethylene glycol or its ester derivative are heated and melted in the presence of a polycondensation catalyst to cause liquid phase polycondensation. 0.7-1.5 dl / g intrinsic viscosity measured in o-chlorophenol
A liquid-phase polycondensation step of producing a polyester (a), and [C] the polyester (a) obtained in the liquid-phase polycondensation step,
A hot water treatment step of contacting with hot water at 60 to 130 ° C. for 5 minutes to 10 hours, and [D-1] the polyester (c) having undergone the above hot water treatment step
A drying step of drying at a temperature of 110 to 150 ° C. for 30 minutes to 6 hours, and [D-2] the polyester (c) having passed through the drying step
A heating step of heating at a temperature of 60 to 200 ° C. for 1 to 10 hours, wherein the acetaldehyde content of the obtained polyester (d) is 10 ppm or less. 2. [A] Liquid-phase polycondensation of a dicarboxylic acid containing terephthalic acid or an ester derivative thereof and a diol containing ethylene glycol or an ester derivative thereof by heating and melting in the presence of a polycondensation catalyst, 0.7-1.5 dl / g intrinsic viscosity measured in o-chlorophenol
A liquid-phase polycondensation step for producing a polyester (a), and [B] the polyester (a) obtained in the liquid-phase polycondensation step,
In an atmosphere at an elevated temperature of crystallization temperature (Tc ₁ ) to 200 ° C.,
A pre-crystallization step of keeping the mixture for 4 minutes to 4 hours, and [C] a polyester (b) having undergone the above-mentioned pre-crystallization step.
Is contacted with hot water at 60 to 130 ° C. for 5 minutes to 10 hours; [D-1] Polyester (c) which has undergone the above hot water treatment step
Drying the polyester at a temperature of 110 ° C. to 150 ° C. for 30 minutes to 6 hours; [D-2]
A heating step of heating at a temperature of 60 to 200 ° C. for 1 to 10 hours, wherein the acetaldehyde content of the obtained polyester (d) is 10 ppm or less. 3. The polyester (a) obtained in the liquid phase polycondensation step [A] has an intrinsic viscosity of 0.8 to 1.2 dl / g measured in o-chlorophenol. The method for producing a polyester according to claim 1. 4. The liquid polycondensation step [A] comprises an esterification reaction step [A-1] and a polycondensation reaction step [A-2], and the polycondensation reaction step [A-2]. The method for producing a polyester according to claim 1 or 2, wherein the method comprises a polycondensation reaction of three or more stages. 5. In the polycondensation reaction step [A-2], the intrinsic viscosity of the polyester obtained after the second-stage polycondensation reaction is 0.4 to 0.7 dl / g. The method for producing a polyester according to claim 4. 6. The polyester according to claim 2, wherein the pre-crystallized polyester (b) obtained in the pre-crystallization step [B] has a crystallinity of 20 to 50%. Method. 7. A polyester (d) having a crystallinity of 30 to 5
Method for producing a polyester according to claim 1 or 2, characterized in that 0%. 8. The method according to claim 1, wherein the content of acetaldehyde in the polyester (d) is 5 ppm or less.