JPH07233252A - Method for producing polyester - Google Patents

Abstract

(57) [Summary] [Object] The present invention can provide a polyester having a small amount of acetaldehyde content and in which acetaldehyde is less likely to increase even when molding a bottle or the like,
Moreover, the present invention provides a method for producing polyester in which the solid-phase polycondensation step can be omitted. [Structure] The method for producing a polyester according to the present invention comprises: [A] a liquid phase for producing a polyester having an intrinsic viscosity of 0.7 to 1.5 dl / g measured in o-chlorophenol by liquid phase polycondensation. The method includes a polycondensation step, a [B] pre-crystallization step, a [C] heating step of heating to a temperature of 160 to 200 ° C. for 1 to 10 hours, and a [D] hot water treatment step. In B] and [C],
The intrinsic viscosity of the polyester is not substantially increased, and (ii) the obtained polyester has an acetaldehyde content of 10 ppm or less.

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 specifically, it is possible to obtain a polyester which has a small amount of acetaldehyde and is less likely to increase acetaldehyde during molding, and further simplifies the production process. To a method for producing a transparent polyester.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION Bottles obtained by biaxially stretch-molding saturated polyester such as polyethylene terephthalate are excellent in transparency, mechanical strength, heat resistance and gas barrier property, and can be used for juices, soft drinks, carbonated drinks, etc. It is widely used as a beverage filling container (PET bottle).

In order to manufacture, for example, a bottle from such polyester, a polyester is usually injection-molded to produce a preform, and the preform is blow-molded to be biaxially stretched and molded into a bottle shape. Is manufactured by.

If acetaldehyde remains in the bottle obtained from polyester as described above, the taste of the content to be filled will be significantly deteriorated. Therefore, it is desirable that the content of acetaldehyde 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, a polyester having a small amount of acetaldehyde before molding and having a small amount of acetaldehyde during molding of the bottle is required.

In the case of polyester, a dicarboxylic acid such as terephthalic acid or an ester derivative thereof is subjected to an esterification reaction with a diol such as ethylene glycol or an ester derivative thereof, and then the esterified product is subjected to a polycondensation reaction in the presence of a polycondensation catalyst. It is manufactured by This polycondensation reaction is carried out 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 with reduced content is obtained.

Thus, in the method for producing polyester,
Although the liquid-phase polycondensation step and the solid-phase polycondensation step must be performed, this solid-phase polycondensation requires a long time, which causes an increase in manufacturing cost.

When the polyester obtained by the liquid phase polycondensation is omitted to produce a molded article such as a bottle as it is by omitting the solid phase polycondensation step, acetaldehyde is produced during molding, and this acetaldehyde is contained in the polyester molded article. There is a problem of remaining.

Therefore, it is possible to provide a polyester which has a small amount of acetaldehyde and is less likely to increase acetaldehyde even when molding a bottle or the like.
Moreover, the appearance of a polyester production method capable of omitting the solid phase polycondensation step is desired.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and provides a polyester which has a small amount of acetaldehyde and does not easily increase acetaldehyde even when molding a bottle or the like. It is an object of the present invention to provide a method for producing a polyester capable of producing a polyester and omitting the solid phase polycondensation step.

[0010]

SUMMARY OF THE INVENTION A method for producing a polyester according to the present invention comprises: [A] heating a dicarboxylic acid containing terephthalic acid or an ester derivative thereof and a diol containing ethylene glycol or an ester derivative thereof in the presence of a polycondensation catalyst. A liquid phase polycondensation step of producing a polyester (a) which is melted and liquid phase polycondensed to have an intrinsic viscosity of 0.7 to 1.5 dl / g measured in o-chlorophenol, [B] Polyester (a) obtained in the liquid phase polycondensation step,
In an atmosphere of elevated temperature crystallization temperature (Tc ₁ ) to 200 ° C., 1
Polyester (b) which has undergone the pre-crystallization step of maintaining for about 4 minutes to [C] and the pre-crystallization step described above.
Is heated to a temperature of 160 to 200 ° C. for 1 to 10 hours, and [D] the polyester (c) which has undergone the above heating step,
A hot water treatment step of contacting with hot water of ~ 130 ° C for 5 minutes to 10 hours. (I) In the steps [B] and [C], the intrinsic viscosity of the polyester is substantially increased. And (ii) the obtained polyester (d) has an acetaldehyde content of 10 ppm or less.

In the production method as described above, 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 a polyester, produce a polyester having a small amount of acetaldehyde and hardly increasing acetaldehyde during molding. You can The polyester obtained in the present invention is suitable as a material for forming preforms and beverage bottles.

[0013]

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

[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 cause liquid phase polycondensation, and o- Intrinsic viscosity measured in chlorophenol is 0.7-1.5 dl / g
And a polyester (a) obtained in the liquid phase polycondensation step [B]
In an atmosphere of elevated temperature crystallization temperature (Tc ₁ ) to 200 ° C., 1
Polyester (b) which has undergone the pre-crystallization step of maintaining for about 4 minutes to [C] and the pre-crystallization step described above.
Is heated to a temperature of 160 to 200 ° C. for 1 to 10 hours, and [D] the polyester (c) which has undergone the above heating step,
A hot water treatment step of contacting with hot water of ~ 130 ° C for 5 minutes to 10 hours. (I) In the steps [B] and [C], the intrinsic viscosity of the polyester is substantially increased. And (ii) the resulting polyester (d) has an acetaldehyde content of 10 ppm or less. 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, a dicarboxylic acid containing terephthalic acid or its ester derivative (eg, lower alkyl ester, phenyl ester, etc.) and ethylene glycol are used. A polyester (a) is produced by melt-melting a diol containing ## STR1 ## or an ester derivative thereof (for example, a monocarboxylic acid ester) in the presence of a polycondensation catalyst and subjecting it to liquid phase polycondensation.

In the present invention, homopolyethylene terephthalate may be produced by using terephthalic acid and ethylene glycol, and dicarboxylic acid containing dicarboxylic acid other than terephthalic acid in an amount of 20 mol% or less in addition to terephthalic acid. It is also possible to produce a copolyester using a diol containing 20 mol% or less of a diol other than ethylene glycol in addition to ethylene glycol.

Specific examples of the dicarboxylic acid other than terephthalic acid used for producing the copolyester include phthalic acid (orthophthalic acid), isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and diphenoxyethanedicarboxylic acid. 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. You may use these in combination of 2 or more types.

Specific examples of diols 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, bisphenols, hydroquinone, aromatic diols such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane and These ester derivatives etc. are mentioned. You may use these in combination of 2 or more types.

Further, 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 is contained in a small amount, for example, 2 mol% or less. Polyesters containing can also be produced. The present invention can be carried out in either a batch system or a continuous system, but the continuous system will be specifically described below.

In the liquid phase polycondensation step [A], the above dicarboxylic acid or its ester derivative (hereinafter,
A polyester is produced by polycondensing a dicarboxylic acid) and a diol or an ester derivative thereof (hereinafter sometimes simply referred to as a diol).
In this liquid phase polycondensation step, first, an esterification reaction of a dicarboxylic acid and a diol is usually performed (esterification reaction step [A-
1]), and then the 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 to 2.0 mol, and preferably 1.03 to 1.5 mol of diol per 1 mol of dicarboxylic acid. This slurry is continuously supplied to the esterification reaction step [A-1].

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

When the esterification reaction step [A-1] is carried out, for example, in two stages, the esterification reaction in the first stage usually has a reaction temperature of 240 to 270 ° C., preferably 245 to 265 ° C.
Pressure 0.2 to 3 kg / cm ² G, preferably 0.5 to ² kg / cm ²
Under the conditions of G, the esterification reaction in the second step is usually carried out at a reaction temperature of 250 to 280 ° C., preferably 255 to 275.
℃, pressure 0-1.5kg / cm ² G, preferably 0-1.3kg
It is carried out under the condition of / cm ² G.

The reaction rate of the esterification reaction in each of these stages is not particularly limited, but it is preferable that the degree of increase in the esterification reaction rate in each stage is smoothly distributed, and further, the esterification reaction of the final stage. In the product, it is usually desired to reach 90% or more, preferably 93% or more.

An esterified product (low-order condensate) is obtained by the above esterification step [A-1], and the number-average molecular weight of this low-order condensate is usually 500 to 5,000. Such an esterification reaction can be carried out without adding an additive other than the dicarboxylic acid and the diol, and can also be carried out in the coexistence of a polycondensation catalyst described later. , Tertiary amines such as tri-n-butylamine, benzyldimethylamine, quaternary ammonium such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide, 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 specific reactor of the first stage or the second stage.

The esterified product thus obtained is
Then, the liquid phase polycondensation reactor is continuously fed. In the liquid phase polycondensation reactor, the polycondensation catalyst is heated under reduced pressure to a temperature not lower than the melting point of the obtained polyester, and the glycol produced at this time is distilled out of the system for polycondensation.

In the present invention, the polycondensation reaction step [A-2] comprises
It may be performed in one step or divided into a plurality of steps.
When the polycondensation reaction step is performed in multiple stages, the first
The polycondensation reaction in the second stage is usually a reaction temperature of 250 to 290 ° C.
It is preferably carried out under the conditions of 260 to 280 ° C and a pressure of 500 to 20 Torr, preferably 200 to 30 Torr, and the polycondensation reaction in the final stage is usually at a reaction temperature of 265 to 300 ° C, preferably 270 to 295 ° C, and a pressure of 10 to 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 one stage before the final stage is conducted under the reaction conditions of the first stage and the final stage. It is carried out under conditions in between. For example, the polycondensation reaction step is 3
If carried out in stages, the second stage polycondensation reaction is
Usually, the reaction temperature is 260 to 295 ° C, preferably 270 to 2
It is carried out at 85 ° C. under a pressure of 50 to 2 Torr, preferably 40 to 5 Torr.

In the present invention, in the liquid phase polycondensation step [A] as described above, the intrinsic viscosity measured in o-chlorophenol at 25 ° C. is 0.7 to 1.5 dl / g, preferably 0.1. A polyester (a) which is 8 to 1.2 dl / g is produced. The intrinsic viscosity reached in each stage except the final 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, in order to produce the polyester (a) having such an intrinsic viscosity,
It is desirable to carry out the polycondensation reaction step [A-2] as described above in three or more stages, preferably in three stages.
The intrinsic viscosity of the polyester supplied to the polycondensation reaction in the second stage is preferably 0.4 to 0.7 dl / g.

In order to obtain the polyester (a) having such an intrinsic viscosity by a multistage polycondensation reaction, known liquid phase polycondensation reactors 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 uniaxial stirrer can be used, and in the third stage, a horizontal reactor having a biaxial stirrer can be used. In addition, in this specification, the intrinsic viscosity is 1.2 g of polyester o-
After being dissolved in 15 ml of chlorophenol by heating, it 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, germanium tetra n-butoxide, antimony catalysts such as antimony trioxide and antimony acetate, and titanium catalysts such as titanium tetrabutoxide can be used.

Of these catalysts, the use of germanium dioxide compounds is preferable because polyesters excellent in hue and transparency can be obtained. Further, the polycondensation reaction is preferably carried out in the presence of a stabilizer.

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

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

The stabilizer is converted into the weight of phosphorus atom in the stabilizer with respect to the total weight of the dicarboxylic acid and the diol,
0.001-0.1% by weight, preferably 0.002-0.
It is preferably used in an amount of 02% by weight. These catalysts and stabilizers can be supplied in the esterification reaction step as described above, or can be supplied to the reactor at the first stage of the polycondensation reaction step. Thus, the polyester obtained from the final liquid phase polycondensation reactor
(a) is usually formed into particles (chip shape) by a melt extrusion molding method.

[B] Pre-Crystallization Step In the present invention, the granular polyester (a) which has undergone the liquid-phase polycondensation step in this manner is pre-crystallized. In this preliminary crystallization step, the granular polyester (a) is heated in a dry state to a temperature of crystallization temperature (Tc ₁ ) to 200 ° C., preferably Tc ₁
It is carried out by keeping the temperature above 180 ° C. for 1 minute to 4 hours.

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

In such a pre-crystallization step, the so-called solid phase polycondensation reaction of 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]. It is almost the same as the intrinsic viscosity of polyester (a). By adding the pre-crystallization step to the polyester in this way, the content of acetaldehyde contained in the polyester can be reduced, and the fusion of granular polyester (chips) in the heat treatment step or hot water treatment step can be prevented. can do.

In the method for producing a polyester according to the present invention, the polyester preliminarily crystallized as described above is used.
The following [C] heating step and then [D] hot water treatment step are added to (b).

[C] Heat Treatment Step In the production method according to the present invention, the granular polyester (b) pre-crystallized as described above is heated at a high temperature. Specifically, the granular polyester is heated to a temperature of 160 to 200 ° C., preferably 170 to 190 ° C. for 1 to 10 hours, preferably 2
Heat for ~ 6 hours. More specifically, polyester
It may be brought into contact with a fluid gas (air, nitrogen gas, etc.) heated to 160 to 200 ° C., preferably 170 to 190 ° C. For example, when the polyester is polyethylene terephthalate, specifically, 160 to 200 ° C.
Preferably, it may be brought into contact with a gas in a fluidized state heated to a temperature of 170 to 190 ° C.

By heating under such conditions,
The acetaldehyde contained in the polyester is removed, and the polyester (c) containing only a trace amount of acetaldehyde is obtained. In this heating process [C], the polycondensation reaction of the polyester hardly progresses, and the intrinsic viscosity of the polyester (c) obtained after the heat treatment is the intrinsic viscosity of the polyester (a) obtained in the liquid phase polycondensation process. It is almost the same as the viscosity.

[D] Hot Water Treatment Step In the production method according to the present invention, hot water treatment is added to the polyester (c) that has undergone the heating step [C]. , Steam, inert gas containing steam, air containing steam, etc.

The contact between the granular polyester (c) and hot water is
Desirably, it is carried out by immersing the polyester in hot water usually heated to a temperature of 60 to 130 ° C, preferably 80 to 100 ° C. The contact between the granular polyester (c) and hot water is usually performed for 5 minutes to 10 hours, preferably 30 minutes to 5 hours. When the granular polyester (c) is brought into contact with steam, steam or steam-containing inert gas or steam-containing air at a temperature of usually 60 to 130 ° C., preferably 80 to 100 ° C.
Granular polyester supplied in an amount of 0.5 g or more per kg
It is carried out by bringing (c) into contact with steam. The contact between the granular polyester and steam is usually 5 minutes to
It is carried out for 10 hours, preferably 1 to 8 hours.

The granular polyester immediately after being subjected to the hot water treatment usually contains water in an amount of 5000 to 10000 ppm. By subjecting the polyester (c) to hot water treatment as described above, it is possible to suppress an increase in acetaldehyde during molding. By subjecting the polyester to hydrothermal treatment in this way, it is possible to suppress an increase in acetaldehyde contained in the polyester at the time of molding because the polycondensation catalyst contained in the polyester, such as a germanium catalyst, can be suppressed by adding hydrothermal treatment to the polyester. Therefore, it is considered that the decomposition reaction or the transesterification reaction hardly progress even when heated during molding, and the amount of acetaldehyde produced is reduced.

Polyester thus treated with hot water
(d) is preferably dried at a low temperature, specifically, 1
At a temperature of 10 to 150 ° C, preferably 120 to 140 ° C,
Desirably, it is dried for 30 minutes to 6 hours, preferably 1 hour to 4 hours. The polyester (d) from which water has been removed by low temperature drying is prevented from being hydrolyzed.

In the method for producing polyester according to the present invention, as described above, [B] pre-crystallization step and [C]
Since the heating step is performed at a lower temperature than the so-called solid-state polymerization step, the polycondensation reaction of the polyester does not substantially proceed, and the intrinsic viscosity of the polyester does not substantially increase in these steps.

The polyester produced according to the present invention has (i) an intrinsic viscosity of 0.
7-1.5 dl / g, preferably 0.8-1.1 dl
/ G Particularly preferably 0.8 to 1.0 dl / g. The polyester produced in the present invention has (ii) acetaldehyde content of 10 ppm or less, preferably 5 ppm or less. The crystallinity of the polyester produced by the present invention is preferably 30 to 50%.

As described above, the polyester obtained by the production method according to the present invention not only has a low acetaldehyde content but also does not easily increase acetaldehyde during molding.
Specifically, the polyester produced by the present invention is injection-molded at a molding temperature of 270 to 310 ° C., for example, 290 ° C., but in the obtained molded product such as preform, the acetaldehyde content is usually 20 ppm or less, preferably Is 1
It is 5 ppm or less.

A bottle obtained by supplying such a polyester to a molding machine such as an injection molding machine to mold 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 rarely changes the taste of the contents.

The polyester produced in the present invention is particularly preferably used as a beverage bottle forming material and a bottle forming preform material.

[0052]

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 which increases during molding. The container does not change the taste of the contents.

Further, in the method for producing a polyester according to the present invention, it is not necessary to perform the solid phase polycondensation step on the polyester, and the productivity and the economy are excellent. Thus, the polyester obtained by the method for producing a polyester according to the present invention is suitable as a material for preforms and beverage bottles.

[0054]

EXAMPLES Next, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples. In this specification, acetaldehyde concentration (ppm)
Is measured on a stepped rectangular plate-shaped molded product as shown in FIG. 2 injection-molded from a polyester chip as follows. The stepped rectangular plate-shaped molded article has a thickness of 2 mm for the A portion, 4 mm for the B portion, 6 mm for the C portion, 3 mm for the D portion, 5 mm for the E portion, and 7 mm for the F portion. Is. Using this part E, the acetaldehyde concentration of the molded product is measured.

Molded and dried polyester chips of the stepped rectangular plate-shaped product are manufactured by Meiki Seisakusho Co., Ltd.
With a -70A injection molding machine, the dew point during molding is -70 ° C.
Of nitrogen is fed to the upper part of the hopper and the screw feeder chute at a rate of 5 Nm ³ / hour, barrel temperature: 290 ° C., C1 / C2 / C3 / nozzle tip temperature of molding machine is 260 ° C./280° C./280 C./300.degree. C. and injection molding under conditions of a mold cooling temperature of 15.degree. C. to obtain a stepped rectangular plate-shaped molded product as shown in FIG. Injection molding of a stepped rectangular plate-shaped molded article is performed by supplying a polyester chip dried from a hopper to an injection molding machine so that the weighing is 12 seconds and the injection is 60 seconds. The residence time of the molten resin in the molding machine is about 72 seconds. The weight of each stepped rectangular plate-shaped molded product is about 75 g.

Acetaldehyde measurement The acetaldehyde concentration of the stepped rectangular plate-shaped molded product was quantified by internal standard method using gas chromatography after extracting the acetaldehyde in the sample with crushing by Freezer Mill. To do. The intrinsic viscosity (dl / g) of the polyester was obtained by dissolving the sample in o-chlorophenol (OCP) by heating, determining the solution viscosity with a capillary viscometer, and the value and the experimental formula prepared in advance.

Measurement of temperature rising crystallization temperature Using a Perkin Elmer DSC-2 differential scanning calorimeter, a sample from the central portion of a polyester chip dried at about 140 ° C. under a pressure of about 5 mmHg for about 5 hours or more. 10 mm
A thin piece of g is sealed in a liquid aluminum pan under a nitrogen atmosphere for measurement. The measurement conditions are as follows: First, the temperature rises rapidly from room temperature, melts and holds at 290 ° C. for 10 minutes, then rapidly cools to room temperature, and then the peak temperature of the exothermic peak detected when the temperature is raised at a temperature rising rate of 10 ° C./min. Ask for.

[0058]

Example 1 100 parts by weight of terephthalic acid, 46.8 parts by weight of ethylene glycol and 0.0 of germanium dioxide.
31 parts by weight was added and the 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 the polycondensation reaction was carried out in three steps. At the final stage, polycondensation reaction was performed at a reaction temperature of 270 ° C. and a reaction pressure of 1 Torr, and an intrinsic viscosity of 0.83 dl
/ G of polyester was obtained. The acetaldehyde concentration of the polyester chip was 53 ppm, and the temperature rising crystallization temperature was 159.0 ° C.

Next, the polyester chips were pre-crystallized at 170 ° C. for 2 hours under a nitrogen stream, heated at 180 ° C. for 3 hours, and then immersed in hot water at 95 ° C. for 3 hours. Then, it was further dried at 130 ° C. for 2 hours at a low temperature. Table 1 shows the intrinsic viscosity, the acetaldehyde concentration and the water content in the polyester chips in each treatment step.

[0060]

[Table 1]

Further, the polyester chip was dried at 160 ° C. for 3 hours under a nitrogen stream to remove water in the chip to 40 pp.
I set it to m. At this time, the chips had an intrinsic viscosity of 0.81 dl / g and an acetaldehyde concentration of 1.7 ppm. Then, it was heated and melted at a temperature of 290 ° C. to form a stepped rectangular plate. The acetaldehyde concentration of the molded product was 12 ppm.

A molding machine M manufactured by Meiki Seisakusho Co., Ltd.
Molding was performed at -100 A 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 8 ppm.

[0063]

Comparative Example 1 Using the same raw material chips as in Example 1, precrystallization was carried out at 170 ° C. for 2 hours under nitrogen flow, and then 180
The mixture was heated at 0 ° C for 3 hours and further dried at 130 ° C for 2 hours at low temperature. After the treatment, the obtained polyester chips had an intrinsic viscosity of 0.82 dl / g and an acetaldehyde concentration of 1.5 ppm. Then, it was dried at 160 ° C. for 3 hours and then heated and melted at a temperature of 290 ° C. to form a stepped rectangular plate. The acetaldehyde concentration of the molded product was 27 ppm. A preform was molded in the same manner as in Example 1 and the acetaldehyde concentration in the preform was measured and found to be 26 ppm.

[0064]

Example 2 Using the same raw material as in Example 1 and treating the polyester chip in the same manner as in Example 1,
After heat treatment was carried out at 170 ° C. for 4 hours, it was immersed in hot water at 95 ° C. for 3 hours. Then, it was further dried at 130 ° C. for 2 hours at a low temperature. Table 2 shows the intrinsic viscosity, acetaldehyde concentration and water content in the chips in each step.

[0065]

[Table 2]

After further drying at 160 ° C. for 3 hours, the temperature is 29.
It was heated and melted at 0 ° C. to form a stepped rectangular plate. The acetaldehyde concentration of the molded product was 13 ppm. A preform was molded by the same method as in Example 1 and the acetaldehyde concentration in the preform was 9 ppm.

[Brief description of 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 rectangular plate formed in the example.

Claims (9)

[Claims] 1. A dicarboxylic acid containing [A] 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 cause liquid phase polycondensation, Intrinsic viscosity measured in o-chlorophenol is 0.7-1.5 dl / g
And a polyester (a) obtained in the liquid phase polycondensation step [B]
In an atmosphere of elevated temperature crystallization temperature (Tc ₁ ) to 200 ° C., 1
Polyester (b) which has undergone the pre-crystallization step of maintaining for about 4 minutes to [C] and the pre-crystallization step described above.
Is heated to a temperature of 160 to 200 ° C. for 1 to 10 hours, and [D] the polyester (c) which has undergone the above heating step,
A hot water treatment step of contacting with hot water of ~ 130 ° C for 5 minutes to 10 hours. (I) In the steps [B] and [C], the intrinsic viscosity of the polyester is substantially increased. And (ii) the resulting polyester (d) has an acetaldehyde content of 10 ppm or less. 2. 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. 3. The liquid phase polycondensation step [A] comprises an esterification reaction step [A-1] and a polycondensation reaction step [A-2]. The polycondensation reaction step [A-2] Is a polycondensation reaction of three or more stages, The method for producing a polyester according to claim 1, wherein 4. In the polycondensation reaction step [A-2], the intrinsic viscosity of the polyester supplied to the final polycondensation reaction is 0.4 to 0.7 dl / g. The method for producing the polyester according to claim 2. 5. The production of polyester according to claim 1, wherein the pre-crystallized polyester (b) obtained in the pre-crystallization step [B] has a crystallinity of 20 to 50%. Method. 6. The polyester (d) has a crystallinity of 30 to 5
It is 0%, The manufacturing method of polyester of Claim 1 characterized by the above-mentioned. 7. The method for producing a polyester according to claim 1, wherein the content of acetaldehyde in the polyester (d) is 5 ppm or less. 8. A preform and a beverage bottle made of the polyester produced by the method for producing a polyester according to claim 1. 9. The preform and beverage bottle according to claim 8, wherein the preform has an acetaldehyde content of 20 ppm or less.