KR19980024491A - Process for producing polyethylene terephthalate - Google Patents

Abstract

The present invention relates to a polyethylene terephthalate production method comprising a liquid phase polycondensation reaction step, a precrystallization step, and a solid phase polycondensation step, wherein the precrystallization step is at least T _{g and not} more than 180 ° C. while stirring the polyethylene terephthalate chip (A). A precrystallization step of heating at a temperature (T ₁ ) to crystallize so that the crystallinity of the polyethylene terephthalate is at least 3%; (B) heating the polyethylene terephthalate at a temperature (T ₂ ) of not less than (T _bm -40 ° C) but not more than T _bm to crystallize the polyethylene terephthalate to at least 30% (where T _bm is The endothermic onset temperature of the bulk in the endothermic peak observed with a differential scanning calorimeter (DSC) when the polyethylene terephthalate is heated at a rate of 10 ° C / min); And (C) heating the polyethylene terephthalate chip with stirring to raise the temperature to the solid state polycondensation temperature. Even in the case of copolymerized polyethylene terephthalate, precrystallization of polyethylene terephthalate can be efficiently achieved.

Description

Polyethylene terephthalate production method

The present invention relates to a method for producing polyethylene terephthalate, and more particularly, to a method for producing polyethylene terephthalate capable of effectively pre-crystallizing polyethylene terephthalate.

Usually, polyethylene terephthalate is manufactured through an esterification process, a liquid phase polycondensation reaction process, and a solid state polycondensation reaction process. However, since the polyethylene terephthalate chip obtained in the liquid phase polycondensation reaction step is amorphous, if the solid phase polycondensation reaction is performed as it is, blocking may occur. Therefore, a preliminary crystallization step is generally provided before the solid phase polycondensation reaction step, and the polyethylene terephthalate obtained through the liquid phase polycondensation step is heated to crystallize and then introduced into the solid phase polycondensation reaction step. However, in order to quickly perform precrystallization, if the polyethylene terephthalate is rapidly heated or heated to a high temperature, blocking or melting of the polyethylene terephthalate chip may occur in the system. Therefore, relatively moderate temperature rise conditions have been conventionally employed.

For example, a method is disclosed in Japanese Patent Laid-Open No. 58-45229, in which polyethylene terephthalate is treated for 1 hour at 150 ° C. under hot air, followed by 2.5 hours under 195 ° C. nitrogen stream. However, such a condition is not preferable because it takes a long time to crystallize, leading to an increase in production cost.

In addition, in the case of a copolymer in which a small amount of comonomer is copolymerized with polyethylene terephthalate, the copolymer has low crystallinity and melting point, so that polyethylene terephthalate can be heated under such conditions to effectively crystallize without causing blocking or melting. This is not known until now.

The present invention has been made in view of the prior art as described above, and an object of the present invention is to provide a method for producing polyethylene terephthalate comprising a precrystallization process capable of effectively pre-crystallizing polyethylene terephthalate copolymerized with polyethylene terephthalate. .

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

2 is a schematic view of a heating apparatus used in the embodiment.

The present invention is a process of pre-crystallizing the polyethylene terephthalate chip by heating the polyethylene terephthalate chip obtained through the esterification step and the liquid polycondensation reaction step, and heating the pre-crystallized polyethylene terephthalate chip above the pre-crystallization temperature In the polyethylene terephthalate production method comprising a solid phase polycondensation reaction step,

The precrystallization process;

(A) a step of crystallizing the polyethylene terephthalate chip at a temperature (T ₁ ) of at least T _g and at most 180 ° C. while stirring to crystallize such that the degree of crystallinity of the polyethylene terephthalate is at least 3%,

(B) a step of crystallizing the polyethylene terephthalate chip at a temperature of (T _bm -40 ° C) or more and T _bm or less (T ₂ ) in a range of at least 30% by crystallinity of the polyethylene terephthalate,

(Where T _bm is the endothermic onset temperature of the bulk in the endothermic peak observed with a differential scanning calorimeter (DSC) when the polyethylene terephthalate is raised at a rate of 10 ° C./min.)

(C) A step of heating the polyethylene terephthalate chip to raise the temperature to the solid state polycondensation temperature.

In the present invention, the process (B) preferably has a final resin temperature of 190 ± 30 ° C. and a heating time of 1 to 3 hours.

In this invention, it is preferable to perform solid-phase polycondensation at 200-230 degreeC temperature.

The polyethylene terephthalate production method according to the present invention will be described in detail below.

In the present invention, the polyethylene terephthalate chip obtained through the esterification step and the liquid polycondensation reaction step is heated to precrystallize the polyethylene terephthalate, and the pre-crystallized polyethylene terephthalate chip is heated above the preliminary crystallization temperature. In the manufacturing method of the polyethylene terephthalate containing the solid-phase polycondensation reaction process mentioned above, the said precrystallization process is performed on the following specific conditions.

Esterification process

The esterification step is usually performed using a slurry containing terephthalic acid and ethylene glycol. The slurry usually contains 1.02 to 2.0 moles, preferably 1.03 to 1.5 moles of ethylene glycol per mole of terephthalic acid. The slurry is fed continuously to the esterification process.

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

Examples of other dicarboxylic acids used in co-condensation in addition to terephthalic acid include aromatic dicarboxylic acids such as phthalic acid (orthophthalic acid), isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and diphenoxytandicarboxylic acid; Aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azeline acid and decandicarboxylic acid; Alicyclic dicarboxylic acid, such as cyclohexanedicarboxylic acid, etc. are mentioned.

Examples of other glycols used for cocondensation in addition to ethylene glycol include aliphatic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol and dodecamethylene glycol; Alicyclic glycols such as cyclohexanedimethanol; Aromatic dihydroxy compounds, such as bisphenol, hydrokinone, and 2, 2-bis (4- (beta) -hydroxyethoxy phenol) proran, etc. are mentioned.

In this invention, it is preferable to use 1-5 mol% of isophthalic acids with respect to a total dicarboxylic acid component in addition to terephthalic acid and isophthalic acid as a dicarboxylic acid component.

The esterification reaction is carried out while the water or alcohol formed by the reaction is removed out of the system from the rectification column under conditions under which ethylene glycol is refluxed using a device in which at least two esterification reactors are connected in series with each other.

The reaction conditions at the time of esterification are the reaction temperature of a 1st-step esterification reaction normally 240-270 degreeC, Preferably it is 245-265 degreeC, and the pressure is usually 0.2-3 kg / cm <^2> -G, Preferably it is 0.5 ˜2 kg / cm ² -G, the reaction temperature of the final esterification reaction is usually 250 to 280 ° C, preferably 255 to 275 ° 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 esterification conditions of the first and second stages are in the range of the first and final stages, and when the esterification reaction is carried out in the third stage or more, The esterification reaction conditions from the second stage to the first stage of the final stage are conditions selected 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 steps, the esterification reaction in the second step usually has a reaction temperature of 245 to 275 ° C, preferably 250 ° C to 270 ° C, and a pressure of 0 to 2 kg / cm. ² -G, preferably 0.2 to 1.5 kg / cm ² -G.

The reaction rate of these esterification reaction is not particularly limited in each step, but it is preferable that the reaction rate gradually increases from the first step to the final step. In addition, it is preferable that the esterification reaction rate at the final stage usually reaches 90% or more, preferably 93% or more.

Such esterification reaction may be carried out without addition of components other than terephthalic acid and ethylene glycol; for example, tertiary amines such as trimethylamine, tri-n-butylamine and benzyldimethylamine; Quaternary ammonium compounds such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzylammonium hydroxide; It can carry out by adding a small amount of basic compounds, such as lithium carbonate, sodium carbonate, potassium carbonate, and sodium acetate. The addition of such a basic compound in the esterification reaction is preferable because the ratio of the dioxyethylene terephthalate component unit in the polyethylene terephthalate main chain can be kept at a relatively low level.

The esterification (lower condensate) is obtained by the said esterification process, and the number average molecular weight of this esterification is 500-5000 normally. The esterification thus obtained is fed to a liquid phase polycondensation reaction process.

Liquid Phase Polycondensation Reaction Process

In the liquid phase polycondensation reaction step, the polycondensation is carried out under reduced pressure in the presence of a polycondensation catalyst at a temperature above the melting point of the obtained polyethylene terephthalate while distilling out the glycol generated at this time.

The liquid phase polycondensation reaction step may be performed in a first step or may be performed in a plurality of steps. In the case where the liquid phase polycondensation reaction step is carried out in plural stages, the polycondensation reaction of the first step is usually performed at a reaction temperature of 250 to 290 ° C, preferably 260 to 280 ° C, and a pressure of 500 to 20 Torr, preferably 200 to The polycondensation reaction in the final stage is carried out under the condition of 30 Torr, and the reaction temperature is usually 265 to 300 ° C, preferably 270 to 295 ° C, and the pressure is usually 10 to 0.1 Torr, preferably 5 to 0.1 Torr, particularly preferred. It is preferably performed under the conditions of 2 to 0.1 Torr.

In the case where the liquid phase polycondensation reaction step is carried out in two stages, the polycondensation reaction conditions of the first and second stages are in the ranges of the first step and the final step, respectively, and the liquid phase polycondensation reaction step is performed in three or more stages. In this case, the polycondensation reaction from the second stage to the first stage of the final stage is performed under the conditions selected between the reaction conditions of the first stage and the reaction conditions of the final stage.

For example, in the case of performing the liquid phase polycondensation reaction step in three stages, the polycondensation reaction in the second stage usually has a reaction temperature of 260 to 295 ° C, preferably 270 to 285 ° C, and a pressure of 50 to 2 Torr, preferably Is carried out under the conditions of 40 to 5 Torr.

Although the intrinsic viscosity (IV) of the polyethylene terephthalate prepared in the liquid phase polycondensation reaction process is not particularly limited, it is preferable that the intrinsic viscosity gradually increases from the first stage to the final stage, and the liquid phase polycondensation of 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 to 0.75 dl / g, more preferably 0.55 to 0.75 dl / g.

Intrinsic viscosity (IV) is calculated from the solution viscosity measured at 25 ° C by heating and dissolving 1.2 g of polyethylene terephthalate in 15 cc of o-chlorophenol.

In addition, the crystallinity of polyethylene terephthalate obtained in the final stage of the liquid polycondensation reactor is usually 2% or less.

It is preferable to perform said liquid-phase polycondensation reaction in presence of a polycondensation catalyst and a stabilizer. As a polycondensation catalyst, germanium compounds, such as germanium dioxide, germanium tetraethoxide, germanium tetra-n-butoxide; Antimony compounds such as antimony trioxide, antimony acetate, antimony tetraethoxide and antimony tetra-n-butoxide; And titanium compounds such as titanium tetrabutoxide and titanium tetrapropoxide. Among these polycondensation catalyst components, germanium dioxide is preferred because of excellent color and transparency of the resulting polyethylene terephthalate. Moreover, when antimony trioxide and antimony acetate are used, since the crystallization rate and color of the produced polyethylene terephthalate are excellent, it is preferable.

Examples of stabilizers include phosphate esters such as trimethyl phosphate, triethyl phosphate, tri-n-butyl phosphate, trioctyl phosphate, triphenyl phosphate and tricresyl phosphate; Phosphorous acid esters such as triphenyl phosphite, trisdodecyl phosphite and trisnonylphenyl phosphite, methyl acid phosphate, isopropyl acid phosphate. Acidic phosphoric acid esters such as butyl acid phosphate, dibutyl phosphate, monobutyl phosphate and dioctyl phosphate; Phosphoric acid; And phosphorus compounds such as polyphosphoric acid. Adding a phosphorus compound to the esterification bath can improve the color and heat resistance stability of the resulting polyethylene terephthalate.

In the present invention, a cobalt compound, a manganese compound, and a magnesium compound may be added in addition to the polycondensation catalyst described above.

Examples of cobalt compounds include cobalt chloride, cobalt sulfate, cobalt hydroxide, cobalt nitrate, cobalt oxalate, cobalt formate, cobalt acetate, cobalt acetylacetonate and cobalt benzoate, and the like. When the cobalt compound is added to the esterification bath, the esterification reaction can be promoted.

Examples of manganese compounds include manganese acetate, manganese acetylacetonate, manganese sulfate, manganese carbonate, manganese nitrate, and the like. The addition of manganese compounds to the esterification bath can promote the esterification reaction.

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

The above-mentioned compounds can usually be added in the form of an aqueous solution, and it is preferable that the amount of water used therein is as small as possible.

The phosphorus compound is usually used at a rate of 5 to 200 ppm, preferably 10 to 100 ppm, as a person with respect to 1 mol of terephthalic acid,

The cobalt compound is usually used at a rate of 5 to 200 ppm, preferably 10 to 60 ppm, as cobalt metal per 1 mol of terephthalic acid,

The manganese mixture is usually used in a ratio of 10 to 200 ppm, preferably 20 to 100 ppm, as a manganese metal per 1 mole of terephthalic acid,

The magnesium compound is usually used at a rate of 5 to 200 ppm, preferably 15 to 50 ppm, as a magnesium metal per 1 mol of terephthalic acid.

The polycondensation catalyst is preferably used in a ratio of 0.0005 to 0.2% by weight, preferably 0.001 to 0.05% by weight, as the metal in the polycondensation catalyst with respect to the weight of the mixture of terephthalic acid and ethylene glycol.

The stabilizer is preferably used at a ratio of 0.001 to 0.1% by weight, preferably 0.002 to 0.02% by weight, as a phosphorus atom in the stabilizer relative to the weight of the mixture of terephthalic acid and ethylene glycol.

These polycondensation catalysts and stabilizers may be supplied in the ester reaction step, or may be supplied to the reactor of the first step of the liquid phase polycondensation reaction step.

The polyethylene terephthalate obtained through the liquid polycondensation reaction step may contain 20 mol% or less of a structural unit derived from dicarboxylic acid other than terephthalic acid or a glycol other than ethylene glycol, in particular It is preferable that the structural unit derived from phthalic acid is contained in 1 to 5 mol% ratio with respect to the whole dicarboxylic acid unit.

In this invention, the content rate of the ethylene terephthalate component unit represented by the following general formula (I) is 95.0-99.9%, and the content rate of the dioxy ethylene phthalate component unit represented by the following general formula (II) is 1.0-5.0% It is preferable that it is the range of.

Polyethylene terephthalate obtained in the final liquid polycondensation reactor is usually formed into a granule (chip) by melt extrusion molding. Chips of polyethylene terephthalate are preferably 2.0 to 5.0 mm, preferably 2.2 to 4.0 mm average particle diameter. In this way, chips of polyethylene terephthalate (hereinafter referred to as PET) having an amorphous or crystallization degree of 3% or less that have undergone the liquid polycondensation reaction process are fed to the precrystallization process.

Precrystallization process

In the precrystallization step, crystallization is performed by heating the PET chip at a temperature at which the solid-phase polycondensation reaction described later or at a temperature lower than the temperature at which the solid-phase polycondensation reaction is performed. Specifically, first, the PET chip is stirred and heated at a temperature of Tg (glass transition point) or more and 180 ° C. or lower, preferably at a temperature (T ₁ ) of 120 to 175 ° C., at least 3% of the crystallinity of polyethylene terephthalate. The process (A) which crystallizes until it becomes is performed.

In the said process (A), it performs using the vertical or horizontal stirring apparatus with a stirring blade. The stirring device is preferably continuous so that PET chips are supplied from one side and discharged to the other side.

The step (A) is performed by, for example, supplying the PET chip from one side of the apparatus using the agitator described above, heating the PET chip with stirring under the flow of a heating gas, and discharging it from the other side.

It is preferable to perform a process (A) in inert gas atmosphere. Nitrogen gas, argon gas, carbon dioxide gas, etc. are mentioned as an inert gas.

The residence time (heating time) of the PET chip in the step (A) is 1 to 20 minutes, preferably 3 to 10 minutes.

Under the PET chip value in the following (T _bm -40 ℃), preferably from (T _bm -30 ℃), particularly preferably (T _bm -20 ℃) above (T _bm) temperature not higher than (T ₂₎ The step (B) is carried out by heating to crystallize the polyethylene terephthalate to at least 30%. Where T _bm is the endothermic onset temperature of the bulk in the endothermic peak observed with a differential scanning calorimeter (DSC) when the polyethylene terephthalate is heated at a rate of 10 ° C / min.

Temperature analysis of the PET chip using a differential scanning calorimeter (DSC) showed that the endothermic peak (main peak) with a larger peak area on the high temperature side and the endothermic peak (small peak) with a smaller peak area on the low temperature side than the main peak were observed. do. In the present invention, the heating temperature in the step (B) is determined by the endothermic start temperature (T _bm ) of the _bulk .

The endothermic peak is obtained by DSC using the following method. That is, a flake of about 10 mmHg of sample taken from the central portion of the PET chip dried at about 140 ° C. under a pressure of about 5 mmHg for about 5 hours or more is placed in a liquid aluminum pan under nitrogen atmosphere. The aluminum pan is then closed, and the endotherm is measured under the following conditions with a differential scanning calorimeter of type DSC-2 manufactured by Perkin Elimer Co. The sample is raised from room temperature at a rate of 10 ° C./min, and the endothermic onset temperature of the detected endothermic peak is obtained. An example of the curve of the DSC of polyethylene terephthalate measured by DSC is shown in FIG.

Unlike step (A), agitation is not performed in step (B). For example, a batch device having a function of supplying, heating, and discharging a PET chip, or a function of supplying a PET chip from one side of the device and discharging the PET chip to its own weight under the flow of a heating gas to be discharged from the other side. A continuous device having a is employed.

Heating under the standing of the PET chip means not stirring the PET chip during the heat treatment, the PET chip is not flowing in the heating apparatus, and the PET chip is moved (flowed) by its own weight in the heating apparatus. Heating in a state where it is present.

When the heating temperature (T ₂ ) is T _{bm or} more, blocking or melting of the PET chip occurs. When the heating temperature is lower than (T _bm- 40 ° C), the crystallization of polyethylene terephthalate may be delayed, which may take a long time for precrystallization.

The endothermic onset temperature T _{bm of the bulk} is moved to the high temperature side with the passage of the heating time, i.e., the progress of crystallization, and therefore, it is preferable to periodically conduct a temperature increase analysis by DSC and to change the heating conditions accordingly. That is, in step (B), it is preferable to set the heating conditions so that the heating temperature of the PET chip gradually rises.

As a preferable temperature condition of process (B), specifically, it is preferable to set so that an initial temperature may be about 150 degreeC and a final temperature may be about 190 degreeC in a batch type, and in continuous type, an inlet temperature is about 150 degreeC and discharge temperature is 190 degree. It is preferable to set the moving speed of the PET chip and the supply amount of the heating gas so as to be about ℃.

It is preferable to perform a process (B) in the same inert gas atmosphere as the said process (A).

The heating time (retention time in continuous type) of the PET chip of the process (B) is 30 minutes-5 hours, Preferably it is 1-3 hours.

Next, a step (C) of raising the PET chip from the temperature (T ₂ ) to the solid phase condensation temperature under stirring is performed.

In this step (C), the same device as the stirring device used in the step (A) can be used. This stirring device is preferably a continuous type so that PET chips are supplied from one side and discharged to the other side.

In the step (C), for example, a stirring device as described above is used to supply the PET chip from one side of the device, and the PET chip is heated while stirring under the flow of a heating gas and discharged to the other side.

It is preferable that the said process (C) is performed in the above inert gas components.

The residence time (heating time) of the PET chip in the step (C) is 1 to 20 minutes, preferably 3 to 10 minutes.

The crystallization degree of the polyethylene terephthalate is at least 30%, preferably at least 45%, by the preliminary crystallization step of the steps (A) to (C). Pre-crystallized PET chip is fed to the solid state polycondensation reaction process.

Solid Phase Polycondensation Reaction Process

The solid-phase polycondensation reaction step is at least one step, the polycondensation temperature is usually 190 to 230 ℃, preferably 195 ℃ to 225 ℃, the pressure is 1Kg / cm ² -G to ¹⁰ Torr, preferably the atmospheric pressure to 10 Torr Under the following conditions. The solid state polycondensation reaction step is usually carried out in a deactivated gas atmosphere such as nitrogen gas, argon gas, carbon dioxide gas, and of these inert gases, nitrogen gas is preferable. Solid phase polymerization can be carried out under high temperature and reduced pressure.

The intrinsic viscosity of the polyethylene terephthalate obtained through the solid phase polycondensation reaction process is usually 0.50 dl / g or more, preferably 0.54 dl / g or more, more preferably 0.70 dl / g or more, particularly preferably 0.72 dl / g or more And the density is usually at least 1.37 g / cm ³ , preferably at least 1.38 g / cm ³ , more preferably at least 1.39 g / cm ³ .

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 0.6% by weight or less, preferably 0.5% by weight or less, more preferably 0.45 Or less, particularly preferably 0.4% or less by weight.

The present invention can effectively pre-crystallize polyethylene terephthalate without blocking or melting of PET chips. Moreover, also in copolymerization polyethylene terephthalate, precrystallization conditions can be easily determined.

Example

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

Example 1

Polyethylene terephthalate (PET) was carried out by performing continuous polycondensation using the continuous polycondensation reaction apparatus in which the first to fourth reactors were coarse and the fifth reactor was a biaxial rotary horizontal reactor. Manufactured

Prepared by mixing 3750 parts by weight of the reaction liquid in advance and mixing high-purity terephthalic acid, ethylene glycol and antimony trioxide in a first reactor maintained at 1.7 Kg / cm ² -G under a nitrogen atmosphere at 255 ° C. under stirring. The slurry was continuously fed at a ratio of 1437 parts by weight of high purity terephthalic acid, 645 parts by weight of ethylene glycol and 0.57 parts by weight of antimony trioxide, to carry out the first step of esterification, during which 203 parts by weight of water and 3 parts by weight of ethylene glycol were used. Was distilled off. The first esterification reaction was controlled so that the average residence time of the slurry was 2.0 hours, and the slurry discharged from the first reactor was maintained at 260 ° C. under 0.8 kg / cm ² -G under stirring. Introduced in two reactors continuously.

In the second reactor, a uniform solution of 85% phosphoric acid and ethylene glycol was continuously fed so that 0.46 parts by weight of 85% phosphoric acid and 9 parts by weight of ethylene glycol were supplied at the same time, while 84 parts by weight of water and 7 parts by weight of ethylene glycol were continuously fed. The distillation removed and continued the esterification reaction of the second step. The two-step esterification reaction was controlled so that the average residence time of the slurry was 2.0 hours, and the slurry discharged from the second reactor was continuously introduced into a third reactor maintained at 275 ° C. and 70 mmHg under stirring.

In the third reactor, 62 parts by weight of ethylene glycol and 6 parts by weight of water were continuously distilled off to perform the first condensation reaction. In addition, the polycondensation reaction of the first step is controlled so that the average residence time of the polycondensation reactants is 1.0 hour, and the polycondensation reactant discharged from the third reactor is kept in a fourth reactor maintained at 280 ° C. and 5 mmHg under stirring. Introduced continuously.

In the fourth reactor, 26 parts by weight of ethylene glycol and 3 parts by weight of water were continuously distilled off to continue the second condensation reaction. In this second step, the polycondensation reaction was controlled so that the average residence time of the polycondensation reactant was 1.0 hour, and the polycondensation reaction product discharged from the fourth reactor was maintained at 282 to 285 ° C and 1.8 to 2.5 mmHg under stirring. To the fifth reactor (biaxial rotary horizontal reactor).

In the fifth reactor, 12 parts by weight of ethylene glycol and 3 parts by weight of water were continuously distilled off to continue the polycondensation reaction of the third step. The third step of the polycondensation reaction is controlled so that the average residence time of the polycondensation reactant is 2.5 hours, continuously taken out onto the strands out of the reactor by the polyester extraction device, immersed in water, and cooled, followed by a strand cutter. Was cut into chips.

Intrinsic viscosity measured at 25 degreeC in the o-chloro phenol of the polyethylene terephthalate obtained by the above-mentioned liquid polycondensation is 0.58 dl / g, content of the diethylene glycol unit is 0.95 weight%, and the crystallinity calculated by the density method is 1 Was%.

Such a polyethylene terephthalate liquid polycondensation product chip is provided with the horizontal continuous heating tank 2, the vertical continuous heating tank 3, the horizontal continuous heating tank 4, and the solid state polycondensation reaction tank 7 as shown in FIG. It was continuously supplied to the reactor, and precrystallization and solid state polycondensation were performed. In Fig. 2, 1 is a supply hopper, 5 is an air purifier, 6 is an air heater, 8 is a cooler, 9 is a nitrogen purifier, 10 is a blower, and 11 is a heater.

General Procedure of Precrystallization

In this reaction apparatus, in the horizontal continuous heating tank 2, a step (A) of supplying a polyethylene terephthalate liquid polycondensation product chip from one side of the heating bath and discharging the polyethylene terephthalate liquid polycondensation product to the other while heating and stirring is performed. All. In the vertical type continuous heating tank 3, a step of supplying a chip of polyethylene terephthalate which has undergone step (A) at the top of the heating bath, heating the chip of polyethylene terephthalate under the flow of nitrogen, and discharging it to the bottom of the heating bath (B). ) Is performed. In this vertical type continuous heating tank 3, polyethylene terephthalate moves in the tank at its own weight. In the horizontal continuous heating tank 4, the process (C) of supplying the chip of the polyethylene terephthalate which passed through the process (B) from one side of the heating tank, and discharging the chip of this polyethylene terephthalate to the other side while heating and stirring is performed.

The polyethylene terephthalate liquid polycondensation product prepared above was supplied to one of the horizontal continuous heating tanks 2, and it stirred, heating at 170 degreeC. The endothermic onset temperature (T _bm ) of the _bulk liquid measured by DSC of polyethylene terephthalate obtained in this step (A) was 175 ° C, and the crystallinity determined by the density method was 41%.

The chip of polyethylene terephthalate manufactured in the next process (A) was supplied to the vertical type continuous heating tank 3, and it heated at 170 degreeC. The residence time in this step (B) was 108 minutes. The degree of crystallinity determined by the density method of polyethylene terephthalate obtained in this step (B) was 48%.

The chip of polyethylene terephthalate manufactured in the next process (B) was supplied to the horizontal type continuous heating tank 4, and it stirred, heating at 202 degreeC. The residence time in this step (C) was 125 minutes. The degree of crystallinity determined by the density method of polyethylene terephthalate obtained in this step (C) was 51%.

The chip of the ethylene terephthalate obtained by such a precrystallization process was heated in a solid state polycondensation reaction apparatus 7 in 210 degreeC nitrogen atmosphere for 15 hours, and solid-phase polycondensation was performed.

In each process, polyethylene terephthalate could be produced without causing fusion.

Example 2

In Example 1, 194 parts by weight of high purity terephthalic acid and 43 parts by weight of isophthalic acid were used instead of 1437 parts by weight of high purity terephthalic acid, except that 0.46 parts by weight of antimony trioxide was added and 0.20 parts by weight of 85% phosphoric acid. In the same manner, polyethylene terephthalate was prepared.

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

The polyethylene terephthalate liquid polycondensation chip produced by the above method was subjected to precrystallization and solid phase polycondensation using a reactor shown in FIG.

First, the polyethylene terephthalate liquid polycondensation chip whose crystallinity degree is 0.9 and temperature is 50 degreeC was supplied to the horizontal continuous heating tank 2 equipped with the stirring blade for process (A). Here, temperature 170 degreeC and residence time were heated at 2.5 minutes. The endothermic initiation temperature (T _bm ) of the _volume measured by DSC of the polyethylene terephthalate obtained by this process (A) was 174 _degreeC . The degree of crystallization of polyethylene terephthalate obtained by the density method was 39%. The exit temperature of the chip of the said process (A) was 165 degreeC. Blocking of the chip in this step (A) did not occur.

Next, the polyethylene terephthalate chip manufactured in the step (A) was supplied to the vertical continuous heating bath 3 for the step (B). The endothermic onset temperature (T _bm ) was 170 ° C. lower than 174 ° C., and the residence time was heated to 118 minutes. The degree of crystallization determined by the density method of polyethylene terephthalate obtained in this step (B) was 45%, T _bm was 185 ° C and the outlet temperature was 170 ° C.

Next, the chip of polyethylene terephthalate obtained at the process (B) was supplied to the horizontal continuous heating tank 3 for a process (C). While stirring, 212 degreeC and residence time were heated at 133 minutes. The degree of crystallinity determined by the density method of polyethylene terephthalate obtained in this step (C) was 48%. The outlet temperature was 209 ° C. In this step (C), no blocking or fusion of chips occurred. Moreover, the said polyethylene terephthalate chip was supplied to the solid state polycondensation reaction tank 7, and the solid state polycondensation reaction was performed. In this step, no blocking or fusion of chips occurred.

Example 3

The chip of polyethylene terephthalate manufactured in the process (A) of Example 2 was supplied to the vertical type continuous heating tank 3 for a process (B). Here, 170 _degreeC lower than endothermic onset temperature ( _Tbm ) of polyethylene terephthalate was heated to 63 minutes. The degree of crystallinity determined by the density method of polyethylene terephthalate obtained in this step (B) was 43%, T _bm was 179 ° C and the outlet temperature was 170 ° C.

The polyethylene terephthalate chip obtained at the process (B) was supplied to the horizontal continuous heating tank 4 for a process (C), stirring. 212 degreeC and residence time were heated to 71 minutes, stirring. The degree of crystallization of polyethylene terephthalate obtained in this step (C) was 49%, measured by the density method, and the outlet temperature was 202 ° C.

The chip of the polyethylene terephthalate obtained in the above-mentioned precrystallization step was heated in a nitrogen atmosphere at 210 ° C. for 15 hours in the solid-phase polycondensation reactor 7 to perform solid-phase polycondensation.

In each process, polyethylene terephthalate can be produced without causing blocking or fusion of chips.

Comparative Example 1

The polyethylene terephthalate liquid polycondensation chip prepared in the same manner as in Example 2 was precrystallized using the reaction apparatus shown in FIG.

The said polyethylene terephthalate liquid polycondensation chip was supplied to the horizontal continuous heating tank 2 equipped with the stirring blade for process (A), and it heated at 170 degreeC here. After 1 minute of residence time, the chip was taken out from the continuous heating bath 2 at the chip temperature of 125 ° C at the outlet. The endothermic initiation temperature (T _bm ) of the polyethylene terephthalate obtained in the step (A) was 160 ° C. as measured by DSC. The crystallinity of this polyethylene terephthalate was 1.6% as measured by the density method.

The polyethylene terephthalate produced in the said process (A) was supplied to the vertical type continuous heating tank 3 for process (B), and it heated at 165 degreeC. However, blocking of the chip occurred and heating by the next process was impossible.

Comparative Example 2

The polyethylene terephthalate liquid polycondensation chip prepared in the same manner as in Example 2 was precrystallized using the reaction apparatus shown in FIG.

The said polyethylene terephthalate liquid polycondensation chip was supplied to the horizontal continuous heating tank 2 for a process (A), and it heated at atmospheric temperature 170 degreeC. After 1.5 minutes of residence time, the chip was taken out from the continuous heating bath 2 at the chip temperature of 135 ° C. The endothermic initiation temperature (T _bm ) of the polyethylene terephthalate obtained in the step (A) was 168 ° C as measured by DSC. The crystallinity of this polyethylene terephthalate was 3% as measured by the density method.

The polyethylene terephthalate produced in the said process (A) was supplied to the vertical type continuous heating tank 3 for process (B), and the endothermic start temperature (T _bm ) was 170 _degreeC higher than 168 _degreeC , and the residence time was heated to 40 minutes. The polyethylene terephthalate obtained in the said process (B) was measured by the density method, and crystallinity was 40%. Blocking of the chip occurred in step (B), and heating of the next step was impossible.

Claims (5)

Pre-crystallization step of crystallizing the polyethylene terephthalate by heating the polyethylene terephthalate chip obtained through the esterification step and the liquid phase polycondensation reaction step, and solid-phase polycondensation heating the pre-crystallized polyethylene terephthalate chip above the pre-crystallization temperature In the polyethylene terephthalate production method comprising a polymerization reaction step, The precrystallization process; (A) a step of crystallizing the polyethylene terephthalate chip at a temperature (T ₁ ) of at least T _g and at most 180 ° C. while stirring to crystallize such that the degree of crystallinity of the polyethylene terephthalate is at least 3%, (B) heating the polyethylene terephthalate at a temperature (T ₂ ) of not less than (T _bm -40 ° C) and not more than T _bm to crystallize such that the degree of crystallinity of the polyethylene terephthalate is at least 30%; Where T _bm is the endothermic onset temperature of the bulk in the endothermic peak observed with a differential scanning calorimeter (DSC) when the polyethylene terephthalate is heated at a rate of 10 ° C./min. (C) A method for producing polyethylene terephthalate, characterized in that it is a step of heating the polyethylene terephthalate chip to raise the temperature to the solid state polycondensation temperature. The method of claim 1, Process for producing polyethylene terephthalate, characterized in that the final resin temperature of step (B) is 190 ± 30 ℃ range. The method according to claim 1 or 2, Polyethylene terephthalate production method characterized in that the heating time in the step (B) is in the range of 1 to 3 hours. The method according to any one of claims 1 to 3, Solid phase polycondensation temperature is a polyethylene terephthalate production method characterized in that the range of 200 ~ 230 ℃. The method of claim 1, The heating conditions of step (B) are characterized in that the polyethylene terephthalate is characterized in that the heating temperature of the polyethylene terephthalate gradually increases to the high temperature side in proportion to the shift of the endothermic onset temperature (T _bm ) of the _bulk when the crystallization of the polyethylene terephthalate proceeds. Phthalate preparation method.