JPH10139873A - Production of polyethylene terephthalate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing polyethylene terephthalate by which even a copolymerized polyethylene terephthalate can efficiently be previously crystallized. SOLUTION: This method for producing polyethylene terephthalate(PET) comprises a step for previous crystallization composed of (A) a step for heating PET chips at a temperature (Tl ) of Tg or above and <=150 deg.C under stirring and partially crystallizing the PET, (B) a step for heating the PET chips at a temperature within the range of (Tbm -40 deg.C) to Tbm under a standing state of the PET chips and crystallizing the PET until the crystallinity thereof attains at least 30% [Tbm is an endothermic starting temperature of the secondary peak in endothermic peaks recognized when increasing the temperature thereof at 10 deg.C/min rate with a differential scanning calorimeter(DSC)] and (C) a step for heating and increasing the temperature to a solid-phase polycondensation temperature under stirring in the method for producing the polyethylene terephthalate comprising a step for liquid-phase polycondensation reaction, the step for previous crystallization step and a step for solid-phase polycondensation reaction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing polyethylene terephthalate, and more particularly, to a method for producing polyethylene terephthalate which can be efficiently precrystallized.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION Polyethylene terephthalate is
Generally, it is produced through an esterification reaction step, a liquid phase polycondensation reaction step, and a solid phase polycondensation reaction step. However, the polyethylene terephthalate chips obtained in the liquid phase polycondensation reaction step are amorphous, so that if they are directly subjected to the solid phase polycondensation reaction step, blocking may occur. For this reason, in general, a preliminary crystallization step is provided before the solid-phase polycondensation reaction step, and the polyethylene terephthalate that has passed through the liquid-phase polycondensation reaction step is heated and crystallized, and then subjected to the solid-phase polycondensation reaction step. I have. If the temperature is increased rapidly or heated at a high temperature in order to quickly perform this pre-crystallization step, the polyethylene terephthalate chip blocks or fuses in the system, so that a relatively gradual temperature increase condition has been achieved. Has been taken.

For example, Japanese Patent Application Laid-Open No. 58-45229 adopts a condition in which crystallization is performed by treating for 1 hour in hot air at 150 ° C. and then for 2.5 hours in a nitrogen stream at 195 ° C. Under these conditions, crystallization takes a long time and the production cost increases, which is not preferable.

In the case of polyethylene terephthalate copolymer containing a small amount of comonomer, the degree of crystallinity and the melting point are reduced. Therefore, heating the polyethylene terephthalate under any conditions can efficiently crystallize without causing blocking. I didn't know if I could let him.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned prior art, and has been made in consideration of the above circumstances. It is an object to provide a method for producing polyethylene terephthalate including steps.

[0006]

SUMMARY OF THE INVENTION The method for producing polyethylene terephthalate according to the present invention comprises a pre-crystallization step of heating and crystallizing a chip of polyethylene terephthalate obtained through an esterification reaction step and a liquid phase polycondensation reaction step; A solid-phase polycondensation reaction step of heating the converted polyethylene terephthalate chips to a temperature equal to or higher than the pre-crystallization temperature, wherein the pre-crystallization step comprises: (A) stirring the polyethylene terephthalate chips; Heating at a temperature (T ₁ ) of not less than Tg and not more than 180 ° C. to crystallize the polyethylene terephthalate until the crystallinity of the polyethylene terephthalate becomes at least 3%;
(B) A polyethylene terephthalate chip is heated to a temperature (T ₂ ) in a range from (T _bm −40 ° C.) to T _{bm while} standing, and the polyethylene terephthalate is crystallized until the degree of crystallinity becomes at least 30%. (Where T _bm is the endothermic onset temperature of the sub-peaks among the endothermic peaks observed when the polyethylene terephthalate is heated at a rate of 10 ° C./min using a differential scanning calorimeter), ( C) The step of heating and raising the temperature of the polyethylene terephthalate chip to the solid-state polycondensation temperature.

In the present invention, the final resin temperature in the step (B) is preferably in the range of 190 ± 30 ° C., and the heating time of polyethylene terephthalate is preferably 1 to 3 hours.

In the present invention, the solid-state polycondensation temperature is 200
It is preferably in the range of -230 ° C.

[0009]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the method for producing polyethylene terephthalate according to the present invention will be specifically described.

In the present invention, a pre-crystallization step of heating and crystallizing the polyethylene terephthalate chips obtained through the esterification reaction step and the liquid phase polycondensation reaction step,
In the method for producing polyethylene terephthalate, which comprises heating the pre-crystallized polyethylene terephthalate to a temperature equal to or higher than the pre-crystallization temperature, a pre-crystallization step is performed under specific conditions.

Esterification Step The esterification step is performed using a slurry containing terephthalic acid and ethylene glycol. In the slurry, ethylene glycol is usually contained in an amount of 1.02 to 2.0 mol, preferably 1.03 to 1.0 mol per 1 mol of terephthalic acid.
It is contained in a proportion of 5 mol. This slurry is continuously supplied to the esterification reaction step.

In the present invention, polyethylene terephthalate is produced from terephthalic acid and ethylene glycol as raw materials, but other dicarboxylic acids and / or other glycols of 20 mol% or less may be used.

Specific examples of the dicarboxylic acid used for copolycondensation other than terephthalic acid include aromatic dicarboxylic acids such as phthalic acid (orthophthalic acid), isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and diphenoxyethanedicarboxylic acid. , Adipic acid, sebacic acid,
Examples thereof include aliphatic dicarboxylic acids such as azelaic acid and decane dicarboxylic acid, and alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

Specific examples of glycols used for copolycondensation other than ethylene glycol include aliphatic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol and dodecamethylene glycol; Alicyclic glycols such as methanol, bisphenols, hydroquinone, 2,2-bis (4-
and aromatic dihydroxy compounds such as (β-hydroxyethoxyphenyl) propane.

In the present invention, as the dicarboxylic acid component, it is preferable to use isophthalic acid in addition to terephthalic acid at a ratio of 1 to 5 mol% based on the total dicarboxylic acid component.
The esterification reaction is carried out using a device in which at least two esterification reactors are connected in series, while removing water or alcohol produced by the reaction outside the system using a rectification column under the condition that ethylene glycol is refluxed. Is done.

The reaction conditions for carrying out the esterification are as follows:
The reaction temperature of the second-stage esterification reaction is usually 240 to 27
0 ° C., preferably 245-265 ° C., and the pressure is usually 0.2-3 kg / cm ² -G, preferably 0.5-2 kg
/ Cm ² -G, and the temperature of the final esterification reaction is usually from 250 to 280 ° C., preferably from 255 to 27 ° C.
The temperature is 5 ° C. and the pressure is usually 0 to 1.5 kg / cm ² -G, preferably 0 to 1.3 kg / cm ² -G.

When the esterification reaction is carried out in two stages, the first and second stage esterification reaction conditions are within the above range, and when the esterification reaction is carried out in three or more stages, the second stage
The reaction conditions for the esterification reaction from the first stage to the stage immediately before the final stage are conditions between the above-mentioned first-stage reaction conditions and final-stage reaction conditions.

For example, when the esterification reaction is carried out in three stages, the second stage esterification reaction usually has a reaction temperature of 245 to 275 ° C., preferably 250 to 270 ° C.
And a pressure of 0 to ² kg / cm ² -G, preferably 0.1 kg / cm ² -G.
^{2 to} 1.5 kg / cm ² -G.

The reaction rates of these esterification reactions are not particularly limited at each stage, but it is preferable that the esterification reaction rates at each stage gradually increase, and further, that the final stage esterification reaction products , Usually 90% or more, preferably 93% or more.

Such an esterification reaction can be carried out without adding any additives other than terephthalic acid and ethylene glycol.
tertiary amines such as n-butylamine and benzyldimethylamine; quaternary ammoniums such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide; lithium carbonate;
Sodium carbonate, potassium carbonate, can be carried out by adding a small amount of a basic compound such as sodium acetate.When such a basic compound is added and carried out, the dioxyethylene terephthalate component unit in the polyethylene terephthalate main chain can be obtained. This is preferable because the ratio can be kept at a relatively low level.

An esterified product (lower condensate) is obtained by the above esterification reaction step, and the number average molecular weight of the esterified product is usually 500 to 5,000. The obtained esterified product is supplied to a liquid phase polycondensation reaction step.

Liquid phase polycondensation reaction step In the liquid phase polycondensation reaction step, the resulting polyethylene terephthalate is heated to a temperature not lower than the melting point of the obtained polyethylene terephthalate under reduced pressure in the presence of a polycondensation catalyst. And polycondensation.

The liquid-phase polycondensation reaction step may be performed in one stage or may be performed in a plurality of stages. When the liquid-phase polycondensation reaction step is performed in a plurality of stages, the first-stage polycondensation reaction usually has a reaction temperature of 250 to 290 ° C., preferably 2 to 290 ° C.
60 to 280 ° C. and pressure of 500 to 20 Torr,
Preferably, the reaction is performed under the conditions of 200 to 30 Torr,
The final stage of the polycondensation reaction usually has a reaction temperature of 265 to 265.
300 ° C., preferably 270-295 ° C., and a pressure of 10-0.1 Torr, preferably 5-0.1 Torr
r, particularly preferably 2 to 0.1 Torr.

When the liquid-phase polycondensation reaction step is carried out in two stages, the first-stage and second-stage polycondensation reaction conditions are respectively within the above ranges, and when carried out in three or more stages, The polycondensation reaction from the second stage to the last stage before the first stage is performed under the conditions between the above-mentioned first stage reaction conditions and the last stage reaction conditions.

When the liquid phase polycondensation reaction step is carried out in three stages, the second stage polycondensation reaction is usually carried out at a reaction temperature of 26.
0-295 ° C, preferably 270-285 ° C, pressure 5
The reaction is performed under the conditions of 0 to 2 Torr, preferably 40 to 5 Torr.

The intrinsic viscosity (IV) of the polyethylene terephthalate produced in the above liquid phase polycondensation reaction step is not particularly limited, but it is preferable that the degree of increase in the intrinsic viscosity in each step is smoothly distributed. The intrinsic viscosity (IV) of polyethylene terephthalate obtained from the liquid-stage polycondensation reactor of the last stage is usually 0.35 to 0.5.
80 dl / g, preferably 0.45 to 0.75 dl /
g, more preferably 0.55 to 0.75 dl / g.

The intrinsic viscosity (IV) was determined by adding 1.2 g of polyethylene terephthalate to 15 cc of o-chlorophenol.
After heating and dissolving in the solution, the solution is cooled and calculated from the solution viscosity measured at 25 ° C.

The crystallinity of polyethylene terephthalate obtained from the last-stage liquid phase polycondensation reactor is usually 2
%. The liquid-phase polycondensation reaction as described above is desirably performed in the presence of a polycondensation catalyst and a stabilizer. As the polycondensation catalyst, germanium dioxide, germanium tetraethoxide, germanium compounds such as germanium tetra n-butoxide, antimony trioxide, antimony acetate, antimony tetraethoxide, antimony catalyst such as antimony tetra n-butoxide or titanium tetrabutoxide, A titanium catalyst such as titanium tetrapropoxide can be used. Among these polycondensation catalysts, it is preferable to use germanium dioxide because the resulting polyethylene terephthalate has excellent hue and transparency. Further, it is preferable to use antimony trioxide or antimony acetate because the resulting polyethylene terephthalate has excellent crystallization speed and hue.

Examples of the stabilizer include phosphoric esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate and tricresyl phosphate; triphenyl phosphite and trisdodecyl phosphite. , Phosphites such as trisnonylphenyl 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 And the like. By adding a phosphorus compound to the esterification reaction tank, the hue and thermal stability of the obtained polyethylene terephthalate can be improved.

In the present invention, a cobalt compound, a manganese compound and a magnesium compound can be added in addition to the above-mentioned polycondensation catalyst. As the cobalt compound, cobalt chloride, cobalt sulfate, cobalt hydroxide, cobalt nitrate, cobalt oxalate, cobalt formate, cobalt acetate,
Cobalt acetylacetone, cobalt benzoate and the like can be mentioned. When a cobalt compound is added to the esterification tank, the esterification reaction can be promoted.

As the manganese compound, manganese acetate,
Manganese acetylacetonate, manganese sulfate, manganese carbonate, manganese nitrate and the like can be mentioned. When a manganese compound is added to the esterification tank, the esterification reaction can be promoted.

Examples of the magnesium compound include magnesium sulfate, magnesium nitrate, magnesium acetate, magnesium chloride, magnesium carbonate, magnesium citrate, magnesium lactate, and magnesium oxalate. When a magnesium compound is added to the esterification tank, the esterification reaction can be promoted.

The above compound is usually added as an aqueous solution, but the amount of water is preferably as small as possible.
The phosphorus compound is usually 5 to 200 ppm, preferably 10 to 10 ppm as phosphorus based on 1 mol of terephthalic acid.
It is used at a ratio of 0 ppm, and the cobalt compound is usually 5 to 5 moles as a cobalt metal with respect to 1 mol of terephthalic acid.
The manganese compound is used in an amount of usually 10 to 200 ppm, preferably 20 to 100 ppm, as a manganese metal, based on 1 mol of terephthalic acid, and the manganese compound is used in an amount of 10 to 60 ppm. It is used at a ratio of usually 5 to 200 ppm, preferably 15 to 50 ppm, as magnesium metal, based on 1 mol of the acid.

The polycondensation catalyst is used in an amount of 0.0005 to 0.2% by weight, preferably 0.001 to 0.2% by weight of the metal in the polycondensation catalyst, based on the weight of the mixture of terephthalic acid and ethylene glycol. Preferably, it is used in a proportion of 05% by weight.

The stabilizer is used in an amount of 0.001 to 0.1% by weight, preferably 0.002 to 0.02% by weight of phosphorus atoms in the stabilizer with respect to the weight of the mixture of terephthalic acid and ethylene glycol. It is desirable to use it in a proportion of weight%.

These polycondensation catalysts and stabilizers can be supplied in the esterification reaction step,
It can also be supplied to the first stage reactor of the liquid phase polycondensation reaction step.

The polyethylene terephthalate obtained through the liquid phase polycondensation reaction step has an amount of the constituent unit derived from dicarboxylic acid other than terephthalic acid and the constituent unit derived from glycol other than ethylene glycol of 20 mol% or less as described above. In particular, it is preferable that the constituent unit derived from isophthalic acid be contained in a proportion of 1 to 5 mol% based on all dicarboxylic acid units.

In the present invention, the content of the ethylene terephthalate component unit represented by the following general formula (I) is 95.0 to 95.0.
It is preferably in the range of 99.0%, and the content of the dioxyethylene terephthalate component unit represented by the following general formula (II) is preferably in the range of 1.0 to 5.0%.

[0039]

Embedded image

The polyethylene terephthalate obtained from the final liquid-phase polycondensation reactor is usually formed into granules (chips) by a melt extrusion molding method. It is desirable that the polyethylene terephthalate chip has an average particle size of usually 2.0 to 5.0 mm, preferably 2.2 to 4.0 mm. The polyethylene terephthalate chips (hereinafter referred to as “PET chips”) that have undergone the liquid phase polycondensation reaction step are amorphous or have a degree of crystallinity of less than 3%, and have a pre-crystallization step. Supplied to

Pre-crystallization Step In the pre-crystallization step, the PET chip is crystallized while being heated to a temperature at which a solid-state polycondensation reaction to be described later is performed or a temperature somewhat lower than the temperature. Specifically, first, PE
While stirring the T chip, the temperature is higher than Tg (glass transition point) and 1
The step (A) of heating at a temperature (T ₁ ) of 80 ° C. or lower, preferably 120 to 175 ° C. to crystallize the polyethylene terephthalate until the crystallinity of the polyethylene terephthalate becomes at least 3% is performed.

As a device used in this step (A), a vertical or horizontal stirring device with a stirring blade can be adopted. The stirring device is preferably of a continuous type in which PET chips are supplied from one side and discharged from the other side.

In the step (A), for example, a PET chip is supplied from one side of the apparatus by using the above-described stirring apparatus, and the PET chip is heated while stirring under the flow of a heating gas.
This is done by discharging from the other.

Step (A) is preferably performed in an inert gas atmosphere. Examples of the inert gas include a nitrogen gas, an argon gas, and a carbon dioxide gas. Residence time of PET chip in step (A) (heating time)
Is 1 to 20 minutes, preferably 3 to 10 minutes.

Next, the PET chip was allowed to stand (T _bm -4
0C), preferably ( _Tbm- 30C), especially ( _Tbm- 2).
0 ° C.) to T _bm (T ₂ )
Step (B) of crystallizing the PET until the crystallinity of PET becomes at least 30% is performed. Here, T _bm is an endothermic start temperature of a sub-peak among endothermic peaks observed when the temperature of the polyethylene terephthalate is increased at a rate of 10 ° C./min using a differential scanning calorimeter (DSC).

When the PET chip is subjected to temperature rise analysis using DSC, an endothermic peak having a large peak area (main peak) on the high temperature side and an endothermic peak having a small peak area (sub-peak) on the lower temperature side are recognized. In the present invention, the heating temperature in the step (B) is determined by the endothermic onset temperature (T _bm ) of the sub-peak.

The endothermic peak by DSC is determined as follows. That is, DSC- manufactured by PerkinElmer, Inc.
Using a type 2 differential scanning calorimeter, about 5 mm at about 140 ° C
A thin section of about 10 mg of a sample collected from the center of the PET chip dried for about 5 hours or more under a pressure of Hg is sealed in a liquid aluminum pan under a nitrogen atmosphere and measured. As the measurement conditions, first, an endothermic start temperature of an endothermic peak detected when the temperature is raised at a rate of 10 ° C./min from room temperature is obtained.
FIG. 1 shows an example of a DSC curve of polyethylene terephthalate measured by DSC.

In this step (B), stirring as in the step (A) is not performed. For example, a batch type apparatus having a function of supplying, heating, and discharging PET chips, or a method of supplying PET chips from one of the apparatuses, so that the PET chips move by their own weight under the flow of a heated gas and are discharged from the other. A continuous device having various functions is employed.

Here, in the present invention, heating under standing means that the PET chips are not agitated during heating, the PET chips are not flowing in the heating device, and the PET chips are not heated in the heating device. And heating in a state of moving (flowing) by its own weight.

If the heating temperature (T ₂ ) is higher than T _bm , PET
Blocking may occur in the chip, and (T _bm −
If the temperature is lower than 40 ° C.), the crystallization of polyethylene terephthalate becomes too slow, and pre-crystallization may take a long time.

The endothermic onset temperature (T _bm ) of the sub-peak moves to the high temperature side as the heating time elapses, that is, as the crystallization progresses.
It is preferable to change the heating conditions based on the result. That is, in the step (B), it is preferable to set the heating conditions so that the heating temperature of the PET chip gradually increases.

The heating conditions for the PET chip in the step (B) are as follows: the batch type has an initial temperature of about 150 ° C.
It is preferable to set the final temperature to be about 190 ° C. In the continuous method, the moving speed of the PET chip and the supply amount of the heating gas are set so that the inlet temperature is about 150 ° C and the outlet temperature is about 190 ° C. Is preferred.

Step (B) is preferably performed in the same inert gas atmosphere as described above. The heating time (residence time in the continuous method) of the PET chip in the step (B) is
It is 30 minutes to 5 hours, preferably 1 to 3 hours.

Next, while stirring the PET chip, the temperature T
Step (C) of elevating the temperature from ₂ to the solid phase polycondensation temperature is performed. In this step (C), the same apparatus as the stirring apparatus used in the step (A) can be employed. The stirring device is preferably of a continuous type in which PET chips are supplied from one side and discharged from the other side.

In the step (C), for example, a PET chip is supplied from one side of the apparatus using the above-described stirring apparatus, and the PET chip is heated while stirring under the flow of a heating gas.
This is done by discharging from the other.

Step (C) is preferably performed in the same inert gas atmosphere as described above. The residence time (heating time) of the PET chip in the step (C) is 1 to 20 minutes, preferably 3 to 10 minutes.

In the preliminary crystallization step consisting of the steps (A) to (C), the polyethylene terephthalate is crystallized so that the degree of crystallinity is at least 30%, preferably 45% or more. Pre-crystallized PET chips
It is supplied to a solid phase polycondensation reaction step.

Solid- State Polycondensation Reaction Step The solid-state polycondensation reaction step comprises at least one stage, and the polycondensation temperature is usually 190 to 230 ° C., preferably 195 to 230 ° C.
25 ° C., and the polymerization time is 1 to 50 hours, preferably 5 to 50 hours.
-20 hours, pressure is usually 1 kg / cm ² -G -10 Torr
r, preferably at normal pressure to 100 Torr. The solid-phase polycondensation reaction step is usually performed in an atmosphere of an inert gas such as nitrogen gas, argon gas, or carbon dioxide gas, and among these inert gases, nitrogen gas is preferable.
In addition, solid-phase polymerization can also be performed under high temperature and reduced pressure.

The intrinsic viscosity of polyethylene terephthalate obtained through the solid-state polycondensation reaction step is usually 0.50 dl
/ G or more, preferably 0.54 dl / g or more, more preferably 0.70 dl / g or more, and particularly preferably 0.72 dl / g or more.
dl / g or more, and the density is usually 1.37 g / cm ³
Above, preferably 1.38 g / cm ³ or more, more preferably 1.39 g / cm ³ or more.

The amount of the oligomer (cyclic trimer of the ethylene terephthalate component unit represented by the general formula (I)) contained in the polyethylene terephthalate is as follows:
0.6% by weight or less, preferably 0.5% by weight or less, more preferably 0.45% by weight or less, particularly preferably 0.4% by weight or less.
% By weight or less.

[0061]

According to the present invention, pre-crystallization of polyethylene terephthalate can be efficiently performed without blocking of a PET chip. Further, even in the case of copolymerized polyethylene terephthalate, the pre-crystallization conditions can be easily determined.

[0062]

EXAMPLES Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

[0063]

Example 1 A continuous polycondensation reaction apparatus comprising a first to fourth reactors of a tank type and a fifth reactor of a biaxial rotary horizontal reactor was operated as follows. Continuous polycondensation was performed to produce polyethylene terephthalate.

In advance, 3750 parts by weight of the reaction solution was retained, and 1.7 kg /
A slurry prepared by mixing high-purity terephthalic acid, ethylene glycol and antimony trioxide was placed in a first reactor maintained under the conditions of cm ² -G, 1437 parts by weight of high-purity terephthalic acid and 645 parts by weight of ethylene glycol per hour. Parts and 0.57 parts by weight of antimony trioxide were continuously supplied to carry out a first-stage esterification reaction. In this first-stage esterification reaction, 2 hours / hour
03 parts by weight of water and 3 parts by weight of ethylene glycol were distilled off. The first-stage esterification reaction product is
The average residence time of the slurry was controlled to be 2.0 hours, and the slurry discharged from the first reactor was stirred,
The mixture was continuously introduced into a second reactor maintained at 260 ° C. and 0.8 kg / cm ² -G.

In the second reactor, a homogeneous solution of 85% phosphoric acid and ethylene glycol is continuously supplied at a rate such that 85% phosphoric acid is 0.46 parts by weight and ethylene glycol is 9 parts by weight per hour. At the same time, 84 parts by weight of water and 7 parts by weight of ethylene glycol were continuously distilled off, and the second-stage esterification reaction was continued. The second-stage esterification reaction is controlled so that the average residence time of the slurry is 2.0 hours, and the slurry discharged from the second reactor is stirred at 275 ° C., 70 ° C.
It was continuously led to a third reactor maintained under the conditions of mmHg.

In the third reactor, 62 parts by weight of ethylene glycol per hour and 6 parts by weight of water were continuously distilled off to carry out the first stage polycondensation reaction. In the first stage polycondensation reaction, the average residence time of the polycondensation reaction product was 1.
The polycondensation product discharged from the third reactor was controlled so as to be 0 hour, and was continuously introduced into the fourth reactor maintained at 280 ° C. and 5 mmHg under stirring.

In the fourth reactor, 26 parts by weight of ethylene glycol per hour and 3 parts by weight of water were continuously distilled off, and the second stage polycondensation reaction was continued. This second
The polycondensation reaction of the stage is controlled so that the average residence time of the polycondensation reaction product is 1.0 hour, and the polycondensation reaction product discharged from the fourth reactor is stirred at 282 to 285 ° C.
The fifth reactor (horizontal twin-screw rotary reaction tank) maintained under a condition of 1.8 to 2.5 mmHg was continuously introduced.

In the fifth reactor, 12 parts by weight of ethylene glycol per hour and 1 part by weight of water were continuously distilled off, and the third stage polycondensation reaction was continued. This third
The second stage polycondensation reaction is controlled so that the average residence time of the polycondensation reaction product is 2.5 hours, and is continuously withdrawn in a strand form outside the reactor by a polyester withdrawing device, and immersed in water. After being cooled down, it was cut into chips by a strand cutter.

The polyethylene terephthalate obtained by the above liquid phase polycondensation in o-chlorophenol at 25 ° C.
Is 0.58 dl / g, the content of diethylene glycol units is 0.95% by weight,
The crystallinity determined by the density method was 1%.

Such a polyethylene terephthalate liquid phase polycondensation product chip is provided with a horizontal continuous heating tank 2, a vertical continuous heating tank 3, a horizontal continuous heating tank 4, and a solid phase polycondensation reaction tank 7 as shown in FIG. The reactor was continuously fed to the reactor for pre-crystallization and solid-phase polycondensation. In FIG. 2, 1 is a supply hopper, 5 is an air purification device, 6 is an air heater, 8
Denotes a cooler, 9 denotes a nitrogen purifier, 10 denotes a blower, and 11 denotes a heater.

General procedure of the pre-crystallization step: In this reactor, in the horizontal continuous heating tank 2, a polyethylene terephthalate liquid phase polycondensation product chip is supplied from one of the heating tanks, and the polyethylene terephthalate liquid phase polycondensation product chip is supplied. (A) of discharging from the other while heating and stirring. In the vertical continuous heating tank 3, a step of supplying the polyethylene terephthalate chips having undergone the step (A) from the upper part of the heating tank, heating the polyethylene terephthalate chips under the flow of nitrogen, and discharging the chips from the lower part of the heating tank ( B) is performed. In this vertical continuous heating tank 3, the polyethylene terephthalate chips move in the tank by their own weight. In the horizontal continuous heating tank 4, a step (C) of supplying the polyethylene terephthalate chips having undergone the step (B) from one of the heating tanks and discharging the polyethylene terephthalate chips from the other while heating and stirring the chips is performed.

A polyethylene terephthalate liquid-phase polycondensation product chip (crystallinity: 1.0%, temperature: 50%) produced from one of the horizontal continuous heating tanks 2 for the step (A) by the above method.
° C) and stirred while heating to an ambient temperature of 170 ° C. The residence time in this step (A) was 3 minutes. The endothermic onset temperature (T _bm ) of the sub-peak of the polyethylene terephthalate obtained in this step (A) measured by DSC was 175 ° C., and the crystallinity determined by the density method was 41%. The temperature of the PET chip at the outlet of step (A) was 170 ° C.

Next, the polyethylene terephthalate chips produced in the step (A) are supplied to the vertical plug flow type continuous heating tank 3 for the step (B), and the atmosphere temperature is set to 170 ° C.
Heated to ° C. The residence time in this step (B) is 10
8 minutes. The degree of crystallinity of the polyethylene terephthalate obtained in this step (B) determined by the density method is 4
8%. Further, T _bm was 183 ° C., and the temperature of the PET chip at the outlet of the step (B) was 170 ° C.

Next, the polyethylene terephthalate chips produced in the step (B) were supplied to the horizontal continuous heating tank 4 for the step (C) and stirred while being heated to an ambient temperature of 212 ° C. The residence time in this step (C) is 125
Seconds. The degree of crystallinity of the polyethylene terephthalate obtained in this step (C) determined by the density method is 51.
%Met.

The polyethylene terephthalate chips obtained by the above pre-crystallization step were heated in a solid-phase polycondensation reaction tank 7 at 210 ° C. in a nitrogen atmosphere for 15 hours to perform solid-phase polycondensation.

In each of the above steps, polyethylene terephthalate could be produced without blocking or fusion.

[0077]

Example 2 In Example 1, high-purity terephthalic acid 14 was used.
Instead of 37 parts by weight, 1394 parts by weight of high-purity terephthalic acid and 43 parts by weight of isophthalic acid were used, the amount of antimony trioxide added was 0.46 part by weight, and the amount of 85% phosphoric acid was 0.20 part by weight. A polyethylene terephthalate was produced in the same manner as in Example 1 except for the above.

The polyethylene terephthalate liquid phase polycondensate had an intrinsic viscosity of 0.60 dl / g measured in o-chlorophenol at 25 ° C., a diethylene glycol unit content of 0.98% by weight, The crystallinity determined by the density method was 1%.

The polyethylene terephthalate liquid-phase polycondensation product chip (crystallinity: 0.9%, temperature: 50 ° C.) produced by the above-mentioned method was subjected to pre-crystallization and solid-phase polymerization using a reactor as shown in FIG. Condensation was performed. First, the polyethylene terephthalate liquid phase polycondensation product chips were supplied to the horizontal continuous heating tank 2 with stirring blades for the step (A). The atmosphere temperature of the heating tank was 170 ° C., and the residence time in the heating tank was 2.5 minutes. The endothermic onset temperature (T _bm ) of the sub-peak of the polyethylene terephthalate obtained in this step (A) measured by DSC was 174 ° C., and the crystallinity determined by the density method was 39%. PET at the exit of step (A)
The temperature of the chip was 165 ° C. In this step (A), fusion of the chips did not occur.

Next, the polyethylene terephthalate chips produced in the step (A) are supplied to the vertical continuous heating tank 3 for the step (B), and the temperature at which the heat absorption starts (T _bm ) is 174 ° C. or lower. Heated at 170 ° C. The residence time of the PET chips in the heating tank 3 was 118 minutes. The crystallinity of the polyethylene terephthalate obtained in this step (B) determined by a density method was 45%. Also, T
_bm was 185 ° C., and the temperature of the polyethylene terephthalate chip at the outlet of the step (B) was 170 ° C.

Next, the polyethylene terephthalate chips produced in the step (B) were supplied to the horizontal continuous heating tank 4 for the step (C) and stirred while being heated at an atmosphere temperature of 212 ° C. The residence time in this step (C) is 133
Seconds. The degree of crystallinity of the polyethylene terephthalate obtained in this step (C) determined by the density method is 48.
%Met. The temperature of the polyethylene terephthalate chip at the outlet of step (C) was 209 ° C. In this step (C), fusion of the PET chips did not occur.
Further, the chips were supplied to the solid-state polycondensation reaction tank 7 to perform a solid-state polycondensation reaction. However, fusion of the chips did not occur.

[0082]

Example 3 The polyethylene terephthalate chips produced in the step (A) of the example 2 were supplied to the vertical plug flow type continuous heating tank 3 for the step (B) and heated at an ambient temperature of 170 ° C. . The residence time of the polyethylene terephthalate chips in the heating tank 3 was 63 minutes. The crystallinity of the polyethylene terephthalate obtained in this step (B) determined by a density method was 43%. Also, T
_bm was 179 ° C., and the temperature of the polyethylene terephthalate chip at the outlet of the step (B) was 170 ° C.

Next, the polyethylene terephthalate chips produced in the step (B) were supplied to the horizontal continuous heating tank 4 for the step (C), and the mixture was stirred while heating at an atmosphere temperature of 212 ° C. The residence time of the polyethylene terephthalate chip in the heating tank 3 was 71 seconds. This step (C)
Of the polyethylene terephthalate obtained by the above method was 49%. The temperature of the polyethylene terephthalate chip at the outlet of step (C) is 20
2 ° C.

The polyethylene terephthalate chips obtained by the above pre-crystallization step were heated in a solid-phase polycondensation reaction tank 7 at 210 ° C. in a nitrogen atmosphere for 15 hours to perform solid-phase polycondensation. In each step, polyethylene terephthalate could be produced without causing fusion.

[0085]

Comparative Example 1 A polyethylene terephthalate liquid phase polycondensation product chip produced in the same manner as in Example 2 was preliminarily crystallized using a reactor as shown in FIG.

The polyethylene terephthalate liquid-phase polycondensation product chips were supplied to the horizontal continuous heating tank 2 with stirring blades for the step (A). The atmosphere temperature of the heating tank was 170 ° C., the temperature of the PET chip at the outlet was 125 ° C., and the residence time in the heating tank was 1 minute. The endothermic onset temperature (T _bm ) of the polyethylene terephthalate obtained in this step (A) is 16
The temperature was 0 ° C., and the crystallinity determined by the density method was 1.6%.

Next, the polyethylene terephthalate chips produced in the step (A) were supplied to the vertical continuous heating tank 3 for the step (B) and heated at 165 ° C., and the chips were fused. The heating in the subsequent steps became impossible.

[0088]

Comparative Example 2 A polyethylene terephthalate liquid-phase polycondensation product chip produced in the same manner as in Example 2 was preliminarily crystallized using a reactor as shown in FIG.

The polyethylene terephthalate liquid phase polycondensation product chips were supplied to the horizontal continuous heating tank 2 with stirring blades for the step (A). The atmosphere temperature of the heating tank was 170 ° C., the temperature of the heating chip at the outlet of the heating tank was 135 ° C., and the residence time in the step (A) was 1.5 minutes. The endothermic onset temperature (T _bm ) of the polyethylene terephthalate obtained in this step (A) was 168 ° C., and the crystallinity determined by the density method was 3%.

Next, the polyethylene terephthalate chips produced in the step (A) are supplied to the vertical plug flow continuous heating tank 3 for the step (B), and the atmosphere temperature is set to 170.
Heated at ° C. The residence time in the heating bath was 40 minutes.
The crystallinity of the polyethylene terephthalate obtained in this step (B) determined by a density method was 40%. Further, T _bm was 175 ° C. The temperature of the polyethylene terephthalate chip at the outlet of step (B) was 170 ° C. Since the chips were fused in the step (B), heating in the subsequent steps became impossible.

[Brief description of the drawings]

FIG. 1 shows an example of a DSC curve of polyethylene terephthalate measured by DSC.

FIG. 2 is a conceptual diagram illustrating a heating device used in an example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Supply hopper 2 ... Horizontal continuous heating tank 3 ... Vertical continuous heating tank 4 ... Horizontal continuous heating tank 5 ... Air purification apparatus 6 ... Air heater 7 ... Solid-state polycondensation reaction tank 8 ... Cooler 9 ... Nitrogen purification apparatus 10: blower 11: heater

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masahiro Kamiya 1-2-1, Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Petrochemical Industry Co., Ltd. (72) Inventor Shoji Hiraoka Kuga-gun, Yamaguchi Prefecture Mitsui Petrochemical Industry Co., Ltd.

Claims (5)

[Claims] 1. A pre-crystallization step in which a polyethylene terephthalate chip obtained through an esterification reaction step and a liquid phase polycondensation reaction step is heated and crystallized, and the pre-crystallized polyethylene terephthalate chip is pre-crystallized. In the method for producing polyethylene terephthalate comprising a solid-phase polycondensation reaction step of heating to a temperature of not lower than the temperature, the preliminary crystallization step comprises: Heating in ₁ ) to crystallize the polyethylene terephthalate until the crystallinity is at least 3%;
(B) A polyethylene terephthalate chip is heated to a temperature (T ₂ ) in a range from (T _bm −40 ° C.) to T _{bm while} standing, and the polyethylene terephthalate is crystallized until the degree of crystallinity becomes at least 30%. (Where T _bm is the endothermic onset temperature of the sub-peak among the endothermic peaks observed when the polyethylene terephthalate is heated at a rate of 10 ° C./min using a differential scanning calorimeter), C) A method for producing polyethylene terephthalate, comprising a step of heating and raising the temperature of a polyethylene terephthalate chip to a solid phase polycondensation temperature. 2. The method for producing polyethylene terephthalate according to claim 1, wherein the final resin temperature in the step (B) is in a range of 190 ± 30 ° C. 3. The heating time in the step (B) is 1 to 3.
3. The method for producing polyethylene terephthalate according to claim 1, wherein the time is 3 hours. 4. The solid-state polycondensation temperature is 200 to 230 ° C.
The method for producing polyethylene terephthalate according to claim 1, wherein 5. In the step (B), the heating temperature of the polyethylene terephthalate chip is gradually increased along with the shift of the endothermic start temperature (T _bm ) of the sub-peak to the higher temperature side as the crystallization of polyethylene terephthalate progresses. The method for producing polyethylene terephthalate according to claim 1, wherein heating conditions are set so as to heat.