JPH08231689A - Method for producing polyethylene terephthalate - Google Patents

Abstract

(57) Abstract: A specific esterification step, a specific liquid phase polycondensation step, a specific solid phase polycondensation step, and the intrinsic viscosity obtained in the solid phase polycondensation step are 0. A polycondensation reaction product having a density of more than 54 dl / g and a density of 1.37 g / cm ³ or more and an oligomer (cyclic trimer) content of 0.50% by weight or less and water at 70 to 110 ° C. for 3 minutes. A method for producing polyethylene terephthalate, which comprises: bringing the polycondensation catalyst contained in polyethylene terephthalate into contact for 5 hours to deactivate it. [Effect] It is possible to obtain polyethylene terephthalate in which the amount of oligomers generated during molding is small and mold stains are less likely to occur.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD OF THE INVENTION The present invention relates to a method for producing polyethylene terephthalate used for forming films, sheets, etc. including bottles, and more specifically, polyethylene terephthalate which is less likely to cause mold stains during molding can be obtained. And a method for producing such polyethylene terephthalate.

[0002]

TECHNICAL BACKGROUND AND PROBLEMS OF THE INVENTION Conventionally, various resins have been adopted as materials for containers of seasonings, oils, beverages, cosmetics, detergents, etc., depending on the type of filling contents and the purpose of use thereof. ing.

[0003] Of these, polyethylene terephthalate is excellent in mechanical strength, heat resistance, transparency and gas barrier properties, and is particularly suitable as a material for beverage filling containers such as juices, soft drinks and carbonated drinks.

[0004] Such polyethylene terephthalate comprises terephthalic acid or an ester-forming derivative thereof,
It can be obtained by subjecting ethylene glycol or its ester-forming derivative to esterification in the presence of an esterification catalyst, liquid-phase polycondensation in the presence of a polycondensation catalyst, and then solid-phase polycondensation. The polyethylene terephthalate is supplied to a molding machine such as an injection molding machine to form a preform for a hollow molded body, and the preform is inserted into a mold having a predetermined shape and stretch blow-molded. ) And then molded into a hollow molded container.

However, the conventionally known polyethylene terephthalate obtained by the above-mentioned production method contains oligomers such as cyclic trimers, and the oligomers such as cyclic trimers are used in a blow mold. Mold contamination is caused by adhering to the inner surface or the gas exhaust port or exhaust pipe of the mold, or the oligomer is adhered to the vent portion of the mold of the injection molding machine as described above, and mold contamination is caused. Had occurred.

[0006] Such mold stains cause rough surface and whitening of the obtained bottle. If the bottle becomes white, it must be discarded. For this reason, when molding a bottle using a conventionally known polyethylene terephthalate, it is necessary to frequently remove mold stains, resulting in a serious problem that the productivity of the bottle is significantly reduced.

In view of the current situation as described above, the present inventors have
As a result of diligent research to obtain polyethylene terephthalate that does not easily cause mold fouling during molding, the main cause of mold fouling during molding is that a large amount of oligomers such as cyclic trimers are generated during molding of polyethylene terephthalate. It was found that the total amount of oligomers such as cyclic trimers contained in polyethylene terephthalate increases.

The inventors of the present invention further studied based on the above findings. As a result, by contacting polyethylene terephthalate obtained by a series of continuous steps with water, the total amount of oligomers such as cyclic trimers at the time of molding was determined. They have found that the increase can be suppressed, and have completed the present invention.

JP-A-59-25815 discloses that polyethylene terephthalate powder is treated with heated steam at 110 ° C. or higher in order to crystallize polyethylene terephthalate prior to solid phase polycondensation of polyethylene terephthalate. A method of doing so is disclosed.

Further, JP-A-59-219328 discloses that the intrinsic viscosity is at least 0.4 dl / g and the density is 1.
Step of controlling the humidity of polyester having ethylene terephthalate unit as a main repeating unit of 35 g / cm ³ or less so that the moisture content is at least 0.2% by weight or more, and pre-crystallization at a temperature of 140 ° C. or more And a step of solid phase polymerization at a temperature of 180 ° C. or higher and 240 ° C. or lower under an inert gas atmosphere or under reduced pressure, is disclosed.

[0011]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problems associated with the prior art as described above, and it is an object of the present invention to provide a polyethylene terephthalate which has a small amount of oligomers formed during molding and is less likely to cause mold contamination. It is an object of the present invention to provide a method for producing polyethylene terephthalate which can be obtained.

[0012]

SUMMARY OF THE INVENTION The method for producing polyethylene terephthalate according to the present invention comprises an esterification step of esterifying terephthalic acid or its ester-forming derivative and ethylene glycol or its ester-forming derivative, and the above-mentioned esterification step. Liquid phase polycondensation step of heating and melting the obtained esterified product in the presence of a polycondensation catalyst, and heating the polycondensation reaction product obtained in the liquid phase polycondensation step to a temperature below the melting point in an inert atmosphere. Solid phase polycondensation step and intrinsic viscosity obtained in the above solid phase polycondensation step is 0.54 dl / g or more, density is 1.37 g / cm ³ or more, and oligomer (cyclic trimer) is contained. The polycondensation reaction product in an amount of 0.50% by weight or less is brought into contact with water at 70 to 110 ° C. for 3 minutes to 5 hours to remove the polycondensation catalyst contained in polyethylene terephthalate. It is characterized by containing a water treatment step of.

[0013] The polyethylene terephthalate obtained by the method for producing polyethylene terephthalate according to the present invention has a small amount of oligomers such as cyclic trimers generated during molding, and therefore is less likely to cause mold contamination.

[0014]

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

The method for producing polyethylene terephthalate according to the present invention comprises an esterification step, a liquid phase polycondensation step of heating and melting the esterified product obtained in the esterification step,
Solid phase polycondensation step of heating the polycondensation reaction product obtained in the liquid phase polycondensation step to a temperature below the melting point, and a water treatment step of contacting the polycondensation reaction product obtained in the solid phase polycondensation step with water Including and

The method for producing polyethylene terephthalate according to the present invention is carried out by using terephthalic acid or its ester-forming derivative and ethylene glycol or its ester-forming derivative as raw materials. The following other dicarboxylic acids and / or other glycols may be copolycondensed.

Specific examples of the dicarboxylic acid used for copolycondensation other than terephthalic acid include aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, naphthalene dicarboxylic acid, diphenyldicarboxylic acid, diphenoxyethanedicarboxylic acid, and adipic acid. , An aliphatic dicarboxylic acid such as sebacic acid, azelaic acid and decanedicarboxylic acid, and an alicyclic dicarboxylic acid such as cyclohexanedicarboxylic acid.

Specific examples of glycols used for copolycondensation other than ethylene glycol include trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol, dodecamethylene glycol and other aliphatic glycols, and cyclohexane. Examples thereof include alicyclic glycols such as dimethanol, bisphenols, hydroquinone, and aromatic diols such as 2,2-bis (4-β-hydroxyethoxyphenyl) propane.

The raw material containing terephthalic acid or its ester-forming derivative as described above and ethylene glycol or its ester-forming derivative is esterified. Specifically, first, a slurry containing terephthalic acid or an ester-forming derivative thereof and ethylene glycol or an ester-forming derivative thereof is prepared.

Such a slurry contains 1.02 mol of terephthalic acid or its ester-forming derivative.
˜1.4 mol, preferably 1.03 to 1.3 mol ethylene glycol or its ester-forming derivatives. This slurry is continuously supplied to the esterification reaction step.

The esterification reaction is carried out by removing at least two esterification reactors in series using an apparatus in which ethylene glycol is refluxed while removing water produced by the reaction from the system in a rectification column. Be implemented. The reaction conditions for carrying out the esterification reaction are such that the temperature of the esterification reaction in the first stage is usually 240 to 270 ° C., preferably 245 to 2
The temperature is 65 ° C., the pressure is usually 0.2 to 3 kg / cm ² G, preferably 0.5 to ² kg / cm ² G, and the temperature of the final stage esterification reaction is usually 250 to 280 ° C., preferably 255. ~ 275 [deg.] C., pressure usually 0-1.5
kg / cm ² G and preferably 0~1.3kg / cm ² G.

Therefore, when the esterification reaction is carried out in two stages, the esterification reaction conditions of the first stage and the second stage are within the above ranges respectively, and when carried out in three or more stages, The reaction conditions for the esterification reaction from the second stage to the stage before the final stage are conditions between the reaction conditions of the first stage and the reaction conditions of the final stage.

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

The reaction rate of these esterification reactions is not particularly limited in each stage, but it is preferable that the increase and the degree of the esterification reaction rate in each stage are smoothly distributed, and further, the final stage. In the esterification reaction product (1), it is usually desired to reach 90% or more, preferably 93% or more.

An esterified product (low-order condensate) is obtained by these esterification steps, and the number average molecular weight of this esterified product is usually 500 to 5,000. Such an esterification reaction can be carried out without adding an additive other than terephthalic acid and ethylene glycol, and can be carried out in the presence of a polycondensation catalyst described later. Tertiary amines such as triethylamine, tri-n-butylamine, and benzyldimethylamine; tetraethylammonium hydroxide;
When quaternary ammonium hydroxide such as butylammonium and trimethylbenzylammonium hydroxide and a basic compound such as lithium carbonate, sodium carbonate, potassium carbonate and sodium acetate are added in a small amount, dioxy in the main chain of polyethylene terephthalate is obtained. It is preferable because the ratio of the ethylene terephthalate component unit can be maintained at a relatively low level.

Then, the obtained esterified product is heated under reduced pressure in the presence of a polycondensation catalyst to a temperature not lower than the melting point of the obtained polyethylene terephthalate, and the glycol produced at this time is distilled out of the system to perform polycondensation. Is supplied to the liquid phase polycondensation step.

The polycondensation reaction in the liquid phase may be carried out in one step or in a plurality of steps. When the reaction is carried out in a plurality of stages, the polycondensation reaction conditions are such that the reaction temperature of the first stage polycondensation is usually from 250 to 290 ° C, preferably from 260 to 280 ° C, and the pressure is usually from 500 to 20 ° C.
Torr, preferably 200 to 30 Torr, the temperature of the final polycondensation reaction is usually 265 to 300 ° C, preferably 270 to 295 ° C, and the pressure is usually 10 to 0.1 Torr.
It is preferably 5 to 0.5 Torr.

When the polycondensation reaction is carried out in two steps,
The polycondensation reaction conditions of the first stage and the second stage are each within the above range, and when the polycondensation reaction is carried out in three or more stages,
The reaction conditions of the polycondensation reaction from the 1st stage to the 1st stage before the final stage are the conditions between the reaction conditions of the 1st stage and the reaction conditions of the final stage.

For example, when the polycondensation reaction is carried out in three stages, the reaction temperature of the second stage polycondensation reaction is usually 2
It is 60 to 295 ° C, preferably 270 to 285 ° C, and the pressure is usually in the range of 50 to 2 Torr, preferably 40 to 5 Torr. The intrinsic viscosity (IV) reached in each of these polycondensation reaction steps is not particularly limited, but it is preferable that the degree of increase in the intrinsic viscosity at each stage is smoothly distributed, and the polycondensation at the final stage The intrinsic viscosity (IV) of polyethylene terephthalate obtained from the reactor is usually 0.35 to 0.80 dl / g, preferably 0.45.
0.75 dl / g, more preferably 0.55 to 0.7
It is preferably in the range of 5 dl / g.

In the present specification, the intrinsic viscosity is 1.2 g of polyethylene terephthalate and 15 g of o-chlorophenol.
It is calculated from the solution viscosity measured at 25 ° C. after being dissolved by heating in cc, followed by cooling.

The density of this polyethylene terephthalate is usually preferably 1.33 to 1.35 g / cm ³ . In the present specification, the density of polyethylene terephthalate is measured at a temperature of 23 ° C. by a density gradient tube using a mixed solvent of carbon tetrachloride and heptane.

The polycondensation reaction as described above is preferably carried out in the presence of a catalyst and a stabilizer. As the catalyst, a germanium compound such as germanium dioxide, germanium tetraethoxide or germanium tetra n-butoxide, an antimony catalyst such as antimony trioxide and a titanium catalyst such as titanium tetrabutoxide can be used. Among these catalysts, the use of a germanium dioxide compound is preferable because the produced polyethylene terephthalate has excellent hue and transparency.

As the stabilizer, phosphoric acid esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate, tricresyl phosphate, triphenyl phosphite, trisdodecyl phosphate, Phosphites such as trisnonylphenyl phosphite, 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. Phosphorus compounds are used.

The proportion of these catalysts or stabilizers used is usually 0.0005 to 0.2 as the weight of the metal in the catalyst in the case of the catalyst, relative to the weight of the mixture of terephthalic acid and ethylene glycol. % By weight, preferably 0.
001 to 0.05% by weight, and in the case of a stabilizer, it is usually 0.0 as the weight of phosphorus atoms in the stabilizer.
It is in the range of 0.01 to 0.1% by weight, preferably 0.002 to 0.02% by weight.

The method for supplying these catalysts and stabilizers is as follows:
It may be supplied at the stage of the esterification reaction step or may be supplied to the first stage reactor of the polycondensation reaction step.

The polyethylene terephthalate used in the present invention contains 20 mol% of a dicarboxylic acid other than terephthalic acid or a diol other than ethylene glycol as described above.
Polyethylene terephthalate, which may be contained in the following amounts, is particularly preferably used in the general formula [I]:

[0037]

Embedded image

The content of the ethylene terephthalate component unit (a) represented by the formula (9) is in the range of 95.0 to 99.0 mol% and the general formula [II]:

[0039]

Embedded image

The content of the dioxyethylene terephthalate component unit (b) represented by is preferably in the range of 1.0 to 5.0 mol%. In this way, the polyethylene terephthalate obtained from the final polycondensation reactor is:
Usually, it is formed into a granular shape (chip shape) by a melt extrusion molding method.

Such granular polyethylene terephthalate is usually 2.0 to 5.0 mm, preferably 2.2 to 5.0 mm.
It is desirable to have an average particle size of 4.0 mm. A solid phase polycondensation step is added to the granular polyethylene terephthalate that has undergone the liquid phase polycondensation step in this manner.

The granular polyethylene terephthalate supplied to the solid phase polycondensation step is preliminarily crystallized by heating it to a temperature lower than the temperature in the case where solid phase polycondensation is carried out in advance.
It may be supplied to a solid phase polycondensation step.

In such a pre-crystallization step, granular polyethylene terephthalate is usually dried at 120 to 20.
It may be carried out by heating to a temperature of 0 ° C., preferably 130 to 180 ° C. for 1 minute to 4 hours, or granular polyethylene terephthalate is usually added under a steam atmosphere or a steam-containing inert gas atmosphere or a steam-containing air atmosphere. You may perform by heating to the temperature of 120-200 degreeC for 1 minute or more.

The solid phase polycondensation step in which such granular polyethylene terephthalate is supplied comprises at least one stage, and the polycondensation temperature is usually 190 to 230 ° C., preferably 1
95-225 ° C, pressure is usually 1 kg / cm ² G
The solid phase polycondensation reaction is carried out under an atmosphere of an inert gas such as nitrogen gas, argon gas, carbon dioxide gas or the like under the conditions of -10 Torr, preferably normal pressure to 100 Torr. Of these inert gases, nitrogen gas is preferred.

The intrinsic viscosity of the polyethylene terephthalate thus obtained is usually 0.54 dl / g or more, preferably 0.70 dl / g or more, particularly preferably 0.7.
It is preferably 2 dl / g or more.

The density of this polyethylene terephthalate is usually 1.37 g / cm ³ or more, preferably 1.38.
It is desirable that it is g / cm ³ or more, and more preferably 1.39 g / cm ³ or more.

Further, the oligomer contained in such polyethylene terephthalate [formula

[0048]

Embedded image

It is desirable that the amount of the above [is a cyclic trimer] is 0.5% by weight or less, preferably 0.45% by weight or less, and particularly preferably 0.40% by weight or less. In the present specification, the amount of the oligomer contained in polyethylene terephthalate is measured as follows.

That is, a predetermined amount of polyethylene terephthalate was dissolved in o-chlorophenol, reprecipitated with tetrahydrofuran and filtered to remove linear polyethylene terephthalate, and then the obtained filtrate was subjected to liquid chromatography (manufactured by Shimadzu Corporation). LC7A) to determine the amount of oligomer contained in polyethylene terephthalate,
This value is divided by the amount of polyethylene terephthalate used in the measurement to obtain the amount of oligomer (wt%) contained in polyethylene terephthalate.

Water treatment is added to the granular polyethylene terephthalate obtained through such a solid phase polycondensation step, and this water treatment is carried out by bringing the granular polyethylene terephthalate into contact with water.

For the contact between the granular polyethylene terephthalate and water, 70% to 1
It is carried out by immersing in hot water at 10 ° C. for 3 minutes to 5 hours. Particularly preferably, it is carried out by immersing granular polyethylene terephthalate in hot water at 80 to 100 ° C. for 5 minutes to 3 hours.

The method of industrially carrying out the contact treatment between the particulate polyethylene terephthalate and water will be illustrated below, but the method is not limited to this. Further, the treatment method may be either a continuous method or a batch method.

When the granular polyethylene terephthalate is subjected to contact treatment with water in a batch system, a silo type treatment apparatus is used. That is, granular polyethylene terephthalate is received in a silo, and water is supplied in a batch method to perform contact treatment. Alternatively, the granular polyethylene terephthalate may be received in a rotating tube type contact treatment device, and the contact treatment may be performed while rotating to make the contact more efficient.

When the granular polyethylene terephthalate is continuously contacted with water, the tower-type processing unit can continuously receive the granular polyethylene terephthalate from the upper portion, and continuously supply water in cocurrent or countercurrent to contact with water. it can. Then, when treated with water, the granular polyethylene terephthalate is drained by a draining device such as a vibrating screener or Simon Carter, and transferred to the next drying step. When treated with steam or a steam-containing gas, it can be directly transferred to the drying step.

For drying the particulate polyethylene terephthalate that has been contact-treated with water, a commonly used drying treatment for polyethylene terephthalate can be used. As a continuous drying method, a hopper type ventilation dryer is generally used in which granular polyethylene terephthalate is supplied from the upper part and a drying gas is aerated from the lower part.

As a method for reducing the amount of dry gas and efficiently drying, a rotary disk type continuous dryer is selected, and heating steam or a heating medium is applied to the rotary disk or the outer jacket while a small amount of dry gas is passed through. It is possible to indirectly heat and dry the granular polyethylene terephthalate by supplying such as.

A double-cone type rotary dryer is used as a dryer for batch-type drying, and it can be dried under a vacuum or under a vacuum while a small amount of dry gas is passed through. Alternatively, it may be dried under atmospheric pressure while aerating a dry gas.

Although atmospheric air may be used as the dry gas, dry nitrogen and dehumidified air are preferable from the viewpoint of preventing a decrease in molecular weight due to hydrolysis of polyethylene terephthalate.

By subjecting polyethylene terephthalate to water treatment as described above, the solid phase polycondensation rate of polyethylene terephthalate is reduced and the polyethylene terephthalate is heated and melted at a temperature of 290 ° C. to form a stepped rectangular plate. It is possible to suppress the subsequent increase in oligomer.

Polyethylene terephthalate thus treated with water has a reduced solid-phase polycondensation rate as described above, but is 215 ° C. in an inert gas atmosphere.
The polycondensation rate when solid phase polycondensation is performed by heating to the temperature of
0.0050 dl / g · hour or less, preferably 0.004
0 dl / g · hour or less, particularly preferably 0.0030 dl
/ G · hour or less is desirable.

In the present specification, the polycondensation rate upon solid phase polycondensation of polyethylene terephthalate is specifically measured as follows. Granular polyethylene terephthalate (60 g) is filled in a cylindrical stainless steel container having an inner diameter of 22 mm and a height of 80 mm and sealed. This container has a nozzle for venting the inert gas at the bottom, and the inert gas is discharged from the top to the outside of the system.

In the solid phase polycondensation, a stainless steel container in which granular polyethylene terephthalate is filled and sealed in a sand bath (manufactured by Japan Percalai Zinc Co., Ltd., aluminum oxide) having a heating device is attached and fixed, and as an inert gas. Carry out with aeration of nitrogen.

The nitrogen used at this time has a dew point of −50 ° C. or lower and an oxygen concentration of 20 ppm or lower, and is preheated to the same bath temperature before being supplied to the stainless steel container. Nitrogen is supplied to the stainless steel container in an amount of 200 N liter (standard condition) per hour.

The sand bath is made to flow by air so that the temperature of the sand bath is uniform and there is no temperature distribution. The heater of the sand bath is controlled by the program controller so that the bath temperature reaches a predetermined solid-phase polycondensation temperature.

The solid-phase polycondensation rate is measured by using the above-mentioned apparatus, specifically by the following method. Granular polyethylene terephthalate was filled and sealed in the cylindrical stainless steel container as described above, fixed in a sand bath, and nitrogen was ventilated at a rate of 200 Nl / hour, and the temperature was raised from room temperature to 170 ° C in 30 minutes. Then, after holding at 170 ℃ for 1 hour, from 170 ℃ to 2
The temperature is raised to 15 ° C. in 30 minutes, and the temperature is further held at 215 ° C. for 4 hours to carry out a solid phase polycondensation reaction.

After the solid-phase polycondensation reaction, the heating was stopped and the temperature in the sand bath was lowered to 70 ° C. with nitrogen aeration.
Then, the stainless container is taken out from the sand bath, and the intrinsic viscosity dl / g (IV) of the solid-phase polycondensed granular polyethylene terephthalate is measured. This IV value is A (dl /
g).

The holding time at 215 ° C. was 20 by the same method.
IV of granular polyethylene terephthalate as a function of time
To measure. Let this IV value be B (dl / g). The solid-state polycondensation rate is calculated by the following equation.

[0069]

[Equation 1]

Where R is the solid phase polycondensation rate (dl / g.
Time) and A and B are IV values (dl / g) after 4 hours and 20 hours, respectively. Further, in the polyethylene terephthalate treated with water as described above, the increase of oligomers in the subsequent molding process is significantly suppressed. This can be confirmed by, for example, measuring the amount of increase in oligomers after polyethylene terephthalate is heated and melted at a temperature of 290 ° C. to form a stepped rectangular plate.

In the water-treated polyethylene terephthalate according to the present invention, specifically, the oligomer increase amount y (% by weight) after heating and melting at a temperature of 290 ° C. to form a stepped rectangular plate is y ≦ −0. .20x + 0.20 Preferably y ≦ −0.20x + 0.18 More preferably y ≦ −0.20x + 0.16.

In the above formula, x is the oligomer concentration (% by weight) before forming the stepped rectangular plate. In this specification, the oligomer increase y (% by weight) after the stepped square plate is formed from the granular polyethylene terephthalate is measured as follows.

That is, 2 k of granular polyethylene terephthalate whose oligomer content was previously measured (measured value X%)
g under the conditions of a temperature of 140 ° C. and a pressure of 10 Torr for 16 hours or more using a tray dryer to reduce the water content of the granular polyethylene terephthalate to 50 ppm or less.

Next, the dried granular polyethylene terephthalate was molded by an M-70A injection molding machine manufactured by Meiki Seisakusho Co., Ltd. at the time of molding with nitrogen having a dew point of -70.degree. Feed at the rate of cubic meters / hour, barrel set temperature 290
℃, the temperature of C1 / C2 / C3 / (nozzle tip) of the molding machine is set to 260/290/290/300 ° C.
Injection molding is performed under a mold cooling temperature of 15 ° C. to obtain a stepped rectangular plate-shaped molded product.

Injection molding of a stepped rectangular plate-shaped molded product is performed by measuring 12
Second, injection is performed for 60 seconds, and the dried granular polyethylene terephthalate is supplied from an hopper to an injection molding machine. The residence time of the molten resin in the molding machine is about 7
2 seconds. The weight of one stepped rectangular plate is 7
It is 5 g, and any one of the 11th to 15th oligomer measurement samples is used after the start of injection molding.

The stepped rectangular plate-shaped molded product 1 has a shape as shown in FIG. 1, and the thickness of the portion A is about 6.5 mm.
The thickness of part B is about 5 mm, and the thickness of part C is about 4 mm. Using this part C, the amount of increase in the oligomer of the molded product is examined.

Next, the molded plate-shaped product having a thickness of 4 mm is cut into chips to obtain oligomer measurement samples. The content of the oligomer of polyethylene terephthalate forming the stepped rectangular plate is measured by the same method as above.

By thus treating the polyethylene terephthalate with water, it is possible to reduce the solid-phase polycondensation rate and suppress the increase of oligomers such as cyclic trimers contained in the polyethylene terephthalate during molding. By subjecting terephthalate to water treatment, the polycondensation catalyst contained in polyethylene terephthalate, such as the germanium catalyst, is deactivated, so that even if it is heated during molding, the decomposition reaction or transesterification reaction hardly progresses, and thus the ring formed The amount of oligomers such as trimers is reduced.

As described above, the polyethylene terephthalate obtained by the production method according to the present invention has a small amount of oligomers such as a cyclic trimer produced at the time of molding, and therefore is supplied to a molding machine such as an injection molding machine. When molding a preform for a hollow molded body, inserting this preform into a mold of a predetermined shape, stretch blow molding, and then heat setting to mold a hollow molded container, oligomers such as cyclic trimers are Dies are less likely to become dirty when attached to the mold.

[0080]

Since the method for producing polyethylene terephthalate according to the present invention includes a step of treating water by bringing it into contact with water, the polyethylene terephthalate obtained by this method is a cyclic trimer produced during molding. The amount of oligomers such as is small, and the total amount of oligomers such as cyclic trimer contained in polyethylene terephthalate at the time of molding is small.

Therefore, the polyethylene terephthalate obtained by the method for producing polyethylene terephthalate according to the present invention does not require frequent washing when producing a molded product, and improves the productivity of molded products such as bottles, films and sheets. It is possible to prevent whitening of the obtained bottle, film or sheet.

[0082]

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

[0083]

Example 1 A continuous polycondensation apparatus comprising a first reactor, a second reactor, a third reactor, a fourth reactor, a fifth reactor of a tank type, and a sixth reactor of a horizontal twin-rotation reactor was used. Polyethylene terephthalate was produced by using the following procedure to carry out continuous polymerization.

In advance, 3750 parts by weight of the reaction solution was retained, and the mixture was stirred at 255 ° C. in a nitrogen atmosphere at 1.7 kg / c.
The slurry prepared by mixing 1437 parts by weight of high-purity terephthalic acid and 645 parts by weight of ethylene glycol every hour was continuously supplied to the first reactor maintained under the condition of m ² G, and the first stage An esterification reaction was performed.

In this first stage esterification reaction, a mixed solution of 203 parts by weight of water and 3 parts by weight of ethylene glycol was distilled off. Further, the esterification reaction product of the first stage was controlled so that the average residence time was 2.0 hours, and 0.8 kg / cm at 260 ° C. under continuous stirring.
It was led to a second reactor maintained under ² G conditions.

In this reactor 2, a homogeneous solution of 0.35 parts by weight of germanium dioxide and 32 parts by weight of ethylene glycol was continuously supplied, and 84 parts by weight of water and 7 parts by weight of an hour were continuously supplied. The mixed solution with ethylene glycol was continuously distilled off, and the second-stage esterification reaction was continued.

The second-stage esterification reaction product was controlled so that the average residence time was 2.0 hours,
It was continuously introduced into a third reactor maintained at 265 ° C. under stirring and normal pressure conditions.

In this third reactor, 1.23 per hour
A homogeneous solution in which 3 parts by weight of trimethyl phosphate and 22 parts by weight of ethylene glycol are mixed is continuously supplied, and a mixed solution of 21 parts by weight of water and 38 parts by weight of ethylene glycol is continuously distilled per hour. And the third-stage esterification reaction was continued.

The esterification reaction product of the third stage was also controlled so that the average residence time was 2.0 hours, and was continuously introduced into the fourth reactor maintained at 70 mmHg at 275 ° C. under stirring. .

In this fourth reactor, a mixture of 62 parts by weight of ethylene glycol and 6 parts by weight of water per hour was continuously distilled off to carry out the first stage polycondensation reaction. In addition, the polycondensation reaction product of the first stage was controlled so that the average residence time was 1.0 hour, and was continuously stirred under 28
It was led to a fifth reactor which was maintained at 5 mm Hg at 0 ° C.

In the fifth reactor, a mixed solution of 26 parts by weight of ethylene glycol and 3 parts by weight of water was continuously distilled off to continue the second-stage polycondensation reaction.
The second-stage polycondensation reaction product is controlled so that the average residence time becomes 1.0 hour, and continuously from 282 ° C.
It was introduced into a sixth reactor which was a horizontal twin-screw rotary reaction tank maintained under the conditions of 1.8 mmHg to 2.5 mmHg at 285 ° C.

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

The intrinsic viscosity IV of polyethylene terephthalate obtained by the above liquid phase polymerization in o-chlorophenol measured at 25 ° C. was 0.57 dl / g, and the content of the dioxyethylene terephthalate component was 2. 5
It was 0 mol%.

Further, the polyethylene terephthalate obtained by the liquid phase polymerization was dried at about 140 ° C. for about 15 hours in a nitrogen atmosphere and crystallized, and then loaded into a tower type solid-state polymerizer and heated at 205 ° C. in a nitrogen atmosphere. Solid phase polymerization was carried out for 15 hours.

The polyethylene terephthalate thus obtained
Solid content of phthalate in o-chlorophenol measured at 25 ° C
Viscosity is 0.80 dl / g and density is 1.40 g / g
cm ³And the oligomer content is 0.31% by weight.
In addition, the inclusion of the dioxyethylene terephthalate component
The amount was 2.53 mol%.

5 kg of polyethylene terephthalate (A) thus obtained was placed in a stainless steel container for 6.5 kg.
It was immersed in kg distilled water. Next, a stainless steel container containing polyethylene terephthalate and distilled water was externally heated, the internal temperature was controlled to 90 ° C., water treatment was carried out by holding for 4 hours, and then dehydration was performed at 140 ° C. for 14 hours in nitrogen. Dried in.

The dried polyethylene terephthalate was diluted with nitrogen in an atmosphere of nitrogen gas as previously described herein.
The polycondensation rate of the solid phase polycondensation treatment by heating to a temperature of 15 ° C. was 0.0026 dl / g · hour.

Further, the oligomer content of the stepped rectangular plate-shaped molded product obtained by molding the polyethylene terephthalate with an injection molding machine of M-70A manufactured by Meiki Seisakusho Co., Ltd. at 290 ° C. was 0.35% by weight. The amount of increase was 0.04% by weight.

[0099]

Comparative Example 1 The polyethylene terephthalate obtained in Example 1 without hot water treatment was heated at 140 ° C.
After drying in nitrogen gas for 2 hours, at 215 ° C under nitrogen atmosphere
The polycondensation rate of the solid-phase polycondensation treatment by heating to the temperature of
It was 0.0067 dl / g · hour.

Further, the polyethylene terephthalate was
The oligomer content of the molded article molded at 0 ° C. was 0.50% by weight, and the increase in oligomer was 0.19% by weight.

[0101]

Example 2 The granular polyethylene terephthalate used in Example 1 was treated with hot water in the same manner as in Example 1, dehydrated and dried, and dried under reduced pressure at 150 ° C. for about 16 hours, and then under a nitrogen atmosphere at Meiki Seisakusho. Co., Ltd. M-100A-SJ type injection molding machine was used to melt at a barrel setting temperature of 280 ° C. and injection molded into a preform mold cooled to 10 ° C. at a molding pressure of 700 kg / cm ² with a diameter of 38 mm. A pleome having a body diameter of 28 mm and a body portion thickness of 4.5 mm and a weight of 64 g was prepared in a molding cycle of 60 seconds.

The oligomer in the preform was 0.35% by weight. Then, only the plug portion was crystallized in an oil bath at 160 ° C. to prepare a preform. Using a biaxial stretch blow molding machine [LB010 manufactured by CORPOPLAST], a blow pressure of about 20 kg / cm ² , a preform heating time of about 60 seconds,
Under the condition of a stretching temperature of 105 ° C., the film is biaxially stretched about 2.2 times in the longitudinal direction and about 3.0 times in the transverse direction, and further held in a mold having a surface temperature of 160 ° C. for 60 seconds, and then the mold is kept for 20 seconds. Heat setting was performed by a method of cooling with water to prepare a biaxially stretched bottle having an inner volume of 1.5 liters, 6 decompression panels in a body, and a bottom-up bottom.

The heating (heat setting) for 60 seconds after stretching was carried out for the purpose of accelerating bottle whitening for evaluation, and the heating (heat setting) time during the production of the bottle was 0.1.
~ 30 seconds is sufficient.

Although 500 bottles were molded, transparent bottles were obtained.

[0105]

Comparative Example 2 The polyethylene terephthalate used in Example 1 was dried and molded in the same manner as in Comparative Example 1 without heat treatment, and in the same manner as in Example 1.

Although 500 bottles were molded in the same manner as in Example 2, a cloudy pattern was generated from about 400 bottles. The oligomer in the obtained preform was 0.
It was 46% by weight.

[Brief description of drawings]

FIG. 1 is a perspective view of a stepped rectangular plate-shaped molded product.

Claims (1)

[Claims] 1. An esterification step of esterifying terephthalic acid or its ester-forming derivative with ethylene glycol or its ester-forming derivative; and the esterified product obtained in the above esterification step in the presence of a polycondensation catalyst. And a solid-phase polycondensation step of heating the polycondensation reaction product obtained in the liquid-phase polycondensation step to a temperature below the melting point in an inert atmosphere, Intrinsic viscosity obtained in the condensation step is 0.54 dl
/ G and a density of 1.37 g / cm ³ or more, and an oligomer (cyclic trimer) content of 0.50
A polyethylene comprising a water treatment step of contacting a polycondensation reaction product of 70% by weight or less with water at 70 to 110 ° C. for 3 minutes to 5 hours to deactivate the polycondensation catalyst contained in polyethylene terephthalate. Method for producing terephthalate.