KR100468794B1 - Manufacturing Method of Polyethylene Terephthalate - Google Patents

Abstract

The present invention provides a terephthalic acid by using an esterification apparatus comprising a plurality of continuous esterification tanks, a liquid phase polycondensation reaction apparatus, and a polyester production apparatus equipped with a solid phase polycondensation reaction apparatus as necessary. Feeding a slurry containing ethylene glycol and antimony compound to the first esterification bath; A method for producing polyethylene terephthalate, comprising the step of adding a phosphorus compound and optionally at least one compound selected from cobalt, magnesium and manganese compounds to a second or subsequent esterification bath. By using this method, polyethylene terephthalate excellent in color and transparency can be produced, which is suitable for producing co-current.

Description

Process for producing polyethylene terephthalate

The present invention relates to a method for producing polyethylene terephthalate, and more particularly to a method for producing polyethylene terephthalate having excellent color and transparency.

Polyethylene terephthalate is widely used, for example, in fibers, films, cocurrent and industrial materials. In particular, in recent years, since polyethylene terephthalate co-current (PET co-current) is often used instead of glass co-current or metal cans, the amount of polyethylene terephthalate used in co-current is increasing. Polyethylene terephthalate for co-current needs to be excellent in extensibility, transparency, color and pressure resistance.

Many methods have been proposed as methods for producing polyethylene terephthalate, and various methods for adding catalysts in the production of polyethylene terephthalate have also been proposed.

For example, Japanese Patent Laid-Open No. 51-91993 describes a method of adding antimony trioxide and phosphorous acid simultaneously in an esterification step. However, when antimony trioxide and phosphorous acid are added at the same time in the esterification process, antimony metal may precipitate, which may deteriorate the color and transparency of the co-current to be prepared from the obtained polyethylene terephthalate.

Japanese Patent Application No. 61-11214 describes a method of separately adding an antimony compound and phosphoric acid triester dissolved in ethylene glycol to another esterification apparatus. However, this method requires an additional device for dissolving the antimony compound in ethylene glycol. In addition, since the antimony compound needs to be heated to a high temperature in order to dissolve it in ethylene glycol, the amount of diethylene glycol increases or worsens the color of the polyethylene terephthalate obtained by thermal history.

As mentioned above, the previously proposed method is not always suitable for the preparation of co-polyethylene terephthalate.

The present invention has been proposed under the above circumstances, and an object of the present invention is to provide a method for producing polyethylene terephthalate, which is excellent in color and transparency, and which can be suitably used for cocurrent production.

The present invention uses a polyester production apparatus including an esterification reaction device comprising a plurality of continuous esterification vessels, a liquid polycondensation reaction device, and a solid state polycondensation reaction device, if necessary,

Feeding a slurry containing terephthalic acid, ethylene glycol and an antimony compound to the first esterification tank,

Provided is a process for producing polyethylene terephthalate, comprising adding a phosphorus compound and, optionally, at least one compound selected from cobalt compounds, magnesium compounds and manganese compounds to a second or subsequent esterification bath.

In the present invention, antimony trioxide is used as the antimony compound. The compounding ratio of the antimony compound is preferably in the range of 150 to 400 ppm relative to terephthalic acid.

The slurry containing terephthalic acid, ethylene glycol, and antimony compound is preferably prepared at a temperature of 0 to 50 ° C.

It is preferable that the reaction temperature of a 1st esterification tank is 240-270 degreeC.

Phosphorus compounds, cobalt compounds, magnesium compounds and manganese compounds can be added in the form of aqueous solutions or ethylene glycol solutions.

In addition to the terephthalic acid as the dicarboxylic acid component, isophthalic acid can be used in an amount of 1 to 3% based on the total dicarboxylic acid components.

Hereinafter, a method for producing polyethylene terephthalate according to the present invention will be described in detail.

In the present invention, a polyethylene terephthalate is produced by using a polyester production apparatus equipped with an esterification reaction device comprising a plurality of continuous esterification baths, a liquid phase polycondensation reaction device, and a solid phase polycondensation reaction device, if necessary.

According to the invention, a slurry containing terephthalic acid, ethylene glycol and antimony compounds is fed to a first esterification bath.

For example, a slurry containing terephthalic acid, ethylene glycol and antimony compounds can be prepared batchwise or continuously using a longitudinal or transverse mixer with a ribbon stirring blade. In this slurry, terephthalic acid and antimony compound are dispersed or suspended in ethylene glycol.

The temperature at the time of preparing a slurry by mixing terephthalic acid, ethylene glycol and an antimony compound is 0-50 degreeC normally, Preferably it is the range of 10-40 degreeC.

In the above temperature range, the antimony compound is hardly dissolved in ethylene glycol, and a slurry in which terephthalic acid and the antimony compound are dispersed or suspended in ethylene glycol is obtained. In addition, ethylene glycol is less likely to deteriorate, and the amount of diethylene glycol produced is also reduced.

This slurry usually contains ethylene glycol in an amount of 1.02 to 2.0 moles, preferably 1.03 to 1.5 moles per 1 mole of terephthalic acid, and 50 to 500 ppm, preferably in terms of antimony metal, per mole of terephthalic acid. Contains an antimony compound in an amount of 150 to 400 ppm.

Examples of antimony compounds include antimony trioxide, antimony acetate, antimony trichloride, and the like. The average particle diameter of the antimony compound is usually about 5 to 20 mesh, preferably about 10 mesh.

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 may be used in an amount of 20 mol% or less.

Examples of dicarboxyl salts other than terephthalic acid used for co-condensation include aromatic dicarboxylic acids such as phthalic acid (allsophthalic acid), isophthalic acid, naphthalenedicarboxylic acid, diphenyldicarboxylic acid and diphenoxyethanedicarboxylic acid. Carboxylic acid; Aliphatic dicarboxylic acids such as adipic acid, sebacic acid, azelanic acid and decandicarboxylic acid; And alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid.

Examples of glycols other than ethylene glycol used for co-condensation include aliphatic glycols such as trimethylene glycol, propylene glycol, tetramethylene glycol, neopentyl glycol, hexamethylene glycol and dodecamethylene glycol; Alicyclic glycols such as cyclohexanedimethanol; And aromatic dihydroxy compounds such as bisphenol, hydroquinone and 2,2-bis (4-β-hydroxyethoxyphenyl) propane.

In this invention, it is good to use isophthalic acid in the quantity of 1-3 mol% with respect to all the dicarboxylic acid components in addition to terephthalic acid as a dicarboxylic acid component.

In the present invention, a phosphorus compound and at least one compound selected from cobalt compounds, magnesium compounds and manganese compounds are added to the second or subsequent esterification tank as necessary.

Examples of the phosphorus compound include phosphoric acid 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; Acidic phosphoric acid esters such as methyl acid phosphate, isopropyl acid phosphate, butyl acid phosphate, dibutyl phosphate, monobutyl phosphate and dioctyl phosphate: phosphoric acid; And polyphosphoric acid. By adding a phosphorus compound to an esterification tank, the color and thermal stability of the polyethylene terephthalate obtained can be improved.

Examples of cobalt compounds include cobalt chloride, cobalt sulfate, cobalt hydroxide, cobalt nitrate, cobalt oxalate, cobalt formate, cobalt acetate, cobalt acetylacetonate and cobalt benzoate. By adding a cobalt compound to the esterification bath, the esterification reaction can be promoted.

Examples of manganese compounds include manganese acetate, manganese acetylacetonate, manganese sulfate, manganese carbonate and manganese nitrate. By adding a manganese compound to an esterification tank, an esterification reaction can be promoted.

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

The compound is usually added as an aqueous solution or ethylene glycol solution. When these are added in aqueous solution, the amount of water is preferably as small as possible.

The phosphorus compound is used in an amount of usually 5 to 200 ppm, preferably 10 to 100 ppm, per mole of terephthalic acid.

The cobalt compound is used in an amount of usually 5 to 200 ppm, preferably 10 to 60 ppm, per mole of terephthalic acid.

The manganese compound is usually used in an amount of 10 to 200 ppm, preferably 20 to 100 ppm per mole of terephthalic acid.

The magnesium compound is used in an amount of usually 5 to 200 ppm, preferably 15 to 50 ppm, per mole of terephthalic acid.

The compound may be added simultaneously or sequentially to a second or subsequent esterification bath, preferably a second esterification bath.

In the present invention, the antimony compound is supplied as a polycondensation catalyst together with terephthalic acid and ethylene glycol to the first esterification tank in the form of a slurry, and a phosphorus compound or the like is added to the second or subsequent esterification tank. Unlike the case of the prior art which simultaneously supplies a phosphorus compound and the like to the esterification bath, precipitation of antimony metal hardly occurs. As a result, polyethylene terephthalate excellent in color and transparency can be obtained.

The esterification reaction is carried out under reflux of ethylene glycol while removing water and alcohol produced by the reaction out of the system by a fractionating column.

As for the reaction conditions which perform esterification, the temperature of the esterification reaction of a 1st step is 240-270 degreeC normally, Preferably it is 245-265 degreeC, and a pressure is 0.2-3 kg / cm <^2> -G normally, Preferably it is 0.5. -2 kg / cm ² -G, and the temperature of the esterification reaction in the final stage 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 Is a condition of 0 to 1.3 kg / cm ² -G.

When the esterification reaction is carried out in two stages, the esterification reaction conditions of the first and second stages are the ranges of the first and final stages respectively. When the esterification reaction is carried out in three or more stages, 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 and final stages.

For example, when the esterification reaction is carried out in three steps, the esterification reaction in the second step is usually 0-2 kg / cm ² -G, preferably at a temperature of 245-275 ° C, preferably 250-270 ° C. It carries out under the pressure of 0.2-1.5 kg / cm <^2> -G.

There is no restriction | limiting in particular in the reaction rate of esterification reaction in each stage, It is good to gradually increase reaction rate for every step. In addition, the esterification reaction rate in the final step is usually 90% or more, preferably 93% or more.

In the esterification reaction, tertiary amines such as trimethylamine, tri-n-butylamine and benzyldimethylamine, quaternary ammoniums such as tetraethylammonium hydroxide, tetra-n-butylammonium hydroxide and trimethylbenzyl ammonium hydroxide, and also lithium carbonate A small amount of basic compounds, such as sodium carbonate, potassium carbonate, and sodium acetate, can be added. The addition of the basic compound in the esterification reaction is preferable in that the ratio of the dioxyethylene terephthalate component in the polyethylene terephthalate backbone can be kept at a relatively low level.

The number average molecular weight of the esterified product (lower condensate) obtained by the above-mentioned esterification step is 500-5,000 normally.

The obtained esterified product is then supplied to a liquid polycondensation reaction apparatus. The antimony compound, phosphorus compound and the like added to the esterification tank are supplied to the liquid phase polycondensation reaction apparatus together with the esterified product in the state dissolved in ethylene glycol.

The liquid phase polycondensation reaction is carried out in the presence of a polycondensation catalyst under heating under a reduced pressure to a temperature higher than the melting point of the polyethylene terephthalate obtained, while distilling and removing the glycol produced during the reaction out of the system.

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

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

For example, when performing the liquid phase polycondensation reaction in three steps, the polycondensation reaction of the second step is usually 50 to 2 Torr, preferably 40 to 5 Torr at a temperature of 260 to 295 ° C, preferably 270 to 285 ° C. Under pressure.

The intrinsic viscosity (IV) of the polyethylene terephthalate produced by the liquid polycondensation reaction is not particularly limited, but it is preferable that the intrinsic viscosity gradually increases from step to step. The intrinsic viscosity (IV) of the polyethylene terephthalate obtained in the final step 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.

The intrinsic viscosity (IV) can be calculated from the solution viscosity measured at 25 ° C. after dissolving 1.2 g of polyethylene terephthalate in 15 cc of o-chlorophenol.

As described above, the polyethylene terephthalate obtained through the liquid polycondensation reaction contains a structural unit derived from dicarboxylic acid other than terephthalic acid and a structural unit derived from glycol other than ethylene glycol in an amount of 20 mol% or less. good. In particular, it is preferable to contain the structural unit derived from isophthalic acid in the quantity of 1-3 mol% with respect to all the dicarboxylic acid units. Polyethylene terephthalates containing isophthalic acid units in amounts in the above range are particularly excellent in color and transparency.

In this invention, the quantity of the ethylene terephthalate component unit represented by following formula (I) is 95.0 to 99.0%, and the dioxyethylene terephthalate component unit represented by following formula (II) is 1.0 to 5.0% of range. It is good to be.

Polyethylene terephthalate obtained from the final liquid polycondensation reaction apparatus is usually formed into granules (chips) by melt extrusion molding. The granular polyethylene terephthalate usually has an average particle diameter of 2.0 to 5.0 mm, preferably 2.2 to 4.0 mm.

The granular polyethylene terephthalate obtained through the liquid polycondensation reaction performs a solid state polycondensation reaction as needed.

The granular polyethylene terephthalate supplied to the solid phase polycondensation reaction apparatus may be precrystallized. Preliminary crystallization is performed by heating granular polyethylene terephthalate to a temperature lower than the solid phase polycondensation reaction temperature. Specifically, the granular polyethylene terephthalate is heated in a dry state at a temperature of usually 120 to 200 ° C, preferably 130 to 180 ° C for 1 minute to 4 hours, or polyethylene terephthalate is steam or steam-containing inert gas. Or it is performed by heating for 1 minute or more at the temperature of 120-200 degreeC normally in a steam containing air atmosphere.

The solid-phase polycondensation reaction is at least one step, usually 1 kg / cm ² -G at a temperature of 190 to 230 ℃, preferably 195 to 225 ℃ It is performed under inert gas atmosphere, such as nitrogen gas, argon gas, or carbon dioxide gas, under the pressure of -10 Torr, Preferably atmospheric pressure -100 Torr. Among these inert gases, nitrogen gas is preferred.

The intrinsic viscosity of the polyethylene terephthalate obtained through the solid state polycondensation reaction 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 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 .

Polyethylene terephthalate is an oligomer (ethylene terephthalate represented by formula (I) above) in an amount of 0.6% by weight or less, preferably 0.5% by weight or less, more preferably 0.45% by weight or less and particularly preferably 0.4% by weight or less. Cyclic trimer).

Next, the present invention will be described in more detail with reference to FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a systematic diagram explaining an example of the manufacturing method of the polyethylene terephthalate which concerns on this invention. In this example, the esterification reaction apparatus 2 is composed of the first esterification tank 21, the second esterification tank 22, and the third esterification tank 23, and the liquid phase polycondensation reaction apparatus 3 is the first. It consists of the liquid polycondensation tank 31 and the 2nd liquid polycondensation tank 32. As shown in FIG.

Terephthalic acid, ethylene glycol and antimony compounds as catalyst are fed to mixer 1 via conduits 11, 12 and 13, respectively, to prepare a slurry. In this slurry, terephthalic acid and an antimony compound are normally dispersed and suspended in ethylene glycol.

The slurry is supplied to the first esterification tank 21 by the feed pump 17. Thereafter, the reaction product in the first esterification tank 21 is supplied to the second esterification tank 22, and the reaction product in the second esterification tank 22 is also supplied to the third esterification tank 23. In each of the first to third esterification tanks 21 to 23, an esterification reaction is performed until a desired esterification rate is obtained. A phosphorus compound, a cobalt compound, etc. are supplied to the 2nd esterification tank 22 through the conduit 14 as needed. The water produced by the esterification reaction is separated from ethylene glycol by means of rectification column 15.

The esterified product thus obtained is continuously extracted from the third esterification tank 23 by the pump 18 and supplied to the first liquid polycondensation tank 31. The reaction product in the first liquid polycondensation tank 31 is supplied to the second liquid polycondensation tank 32. In each of the 1st and 2nd liquid-phase polycondensation tanks 31 and 32, liquid-phase polycondensation reaction is performed until it reaches a desired intrinsic viscosity. The glycol produced by the liquid phase polycondensation reaction is removed by the separator 16.

The polyethylene terephthalate obtained from the second liquid polycondensation reaction apparatus 32 is supplied to the extruder 4 and molded into granules.

Granular polyethylene terephthalate is supplied to the solid-phase polycondensation reaction apparatus 5, and solid-phase polycondensation reaction is performed.

EXAMPLE

The present invention is further illustrated by the following examples, but the present invention is not limited to these examples.

Example 1

By using the continuous polycondensation reaction device which consists of a model 1st-4th reaction apparatus and a horizontal biaxial rotary 5th reaction apparatus, the polycondensation of ethylene glycol and terephthalic acid was performed continuously by the following method, and a polyethylene Terephthalate (PET) was prepared.

Under stirring, in a nitrogen atmosphere, 3,750 parts by weight of the reaction solution was previously held in the first reaction apparatus maintained at 255 ° C and 1.7 kg / cm ² -G. A slurry prepared by mixing high purity terephthalic acid, ethylene glycol and antimony trioxide so as to be fed at a rate of 1,437 parts by weight / hour, ethylene glycol at a rate of 645 parts by weight / hour, and antimony trioxide at a rate of 0.57 parts by weight / hour. It was continuously supplied to the 1st reaction apparatus, and the esterification reaction of the 1st step was performed. During this first esterification reaction, water was distilled and removed out of the system at a rate of 203 parts by weight / hour and ethylene glycol at a rate of 3 parts by weight / hour. In this first step of esterification, the average residence time of the slurry was controlled to be 2.0 hours. The slurry discharged from the first reactor was continuously introduced into the second reactor maintained at 260 ° C. and 0.8 kg / cm ² -G under stirring.

The second reactor was continuously supplied with a homogeneous solution of 85% phosphoric acid and ethylene glycol at a rate of 0.46 parts by weight per hour and ethylene glycol at a rate of 9 parts by weight per hour. Ethylene glycol was continuously distilled and removed out of the system at a rate of 7 parts by weight / hour, and a second step of esterification reaction was performed. In this second stage esterification reaction, the average residence time of the slurry was controlled to be 2.0 hours. The slurry discharged from the second reaction apparatus was continuously introduced into the third reaction apparatus maintained at 70 mmHg at 275 ° C under stirring.

In the third reactor, ethylene glycol and water were continuously distilled and removed out of the system at a rate of 62 parts by weight / hour and a rate of 6 parts by weight / hour, respectively, to carry out the first condensation reaction. The polycondensation reaction of this first step was controlled such that the average residence time of the reaction mixture was 1.0 hour. The polycondensation reaction product discharged | emitted from the 3rd reaction apparatus was continuously introduce | transduced into the 4th reaction apparatus maintained at 5 mmHg at 280 degreeC under stirring.

In the fourth reaction apparatus, ethylene glycol and water were continuously distilled and removed from the system at a rate of 26 parts by weight / hour and a rate of 3 parts by weight / hour, respectively, to carry out the second condensation reaction. The polycondensation reaction of this second step was controlled such that the average residence time of the polycondensation reaction product was 1.0 hour. The polycondensation reactant discharged | emitted from the 4th reaction apparatus was continuously introduced into the 5th reaction apparatus (horizontal biaxial rotary reactor) hold | maintained at 282-285 degreeC and 1.8-2.5 mmHg under stirring.

In the fifth reaction apparatus, ethylene glycol and water were continuously distilled and removed out of the system at a rate of 12 parts by weight / hour and a rate of 1 part by weight / hour, respectively, to carry out the third step of polycondensation reaction. The polycondensation reaction of this third stage was controlled such that the average residence time of the polycondensation reactant was 2.5 hours. The polycondensation reactant discharged from the fifth reaction apparatus is continuously drawn out of the reaction apparatus onto the strand by a polyester drawing apparatus, immersed in water, cooled, and cut into chips by a strand cutter. Polyethylene terephthalate (PET) was obtained.

In o-chlorophenol of PET obtained by the above-mentioned liquid polycondensation, the intrinsic viscosity measured at 25 degreeC was 0.58 dl / g, and diethylene glycol unit content was 0.95 weight%.

Thereafter, PET obtained by liquid polycondensation was subjected to solid phase polymerization at about 210 ° C. for 8 hours under a nitrogen atmosphere. The intrinsic viscosity measured at 25 ° C in the o-chlorophenol of PET thus obtained was 0.79 dl / g, and the density was 1.40 g / cm ³ .

The diethylene glycol unit content of this PET was 0.96 weight%.

This PET was molded at 290 ° C. with an injection molding machine (M-70A manufactured by Meiki Seisakusho) to obtain an end plate-shaped molded product. The haze of this molding was 5.5% at 4 mm thickness and 14.3% at 5 mm thickness. The acetaldehyde content of the endplate-shaped molding obtained by molding PET at 275 ° C was 8 ppm.

Example 2

Instead of 1,437 parts by weight of high purity terephthalic acid, 1,394 parts by weight of high purity terephthalic acid and 43 parts by weight of isophthalic acid were used, except that the amount of antimony trioxide was changed to 0.46 parts by weight, and the amount of 85% phosphoric acid was changed to 0.20 parts by weight. PET was prepared in the same manner as in.

Intrinsic viscosity measured at 25 degreeC in obtained PET (liquid polycondensation product) and o-chlorophenol was 0.60 dl / g, and diethylene glycol unit content was 0.98 weight%.

Thereafter, PET (liquid polycondensation product) was subjected to solid phase polycondensation in the same manner as in Example 1. In o-chlorophenol of obtained PET, the intrinsic viscosity measured at 25 degreeC was 0.85 dl / g, the density was 1.40 g / cm <^3> , and diethylene glycol unit content was 0.98 weight%.

From this PET, two end plate-shaped molded articles were molded in the same manner as in Example 1. The haze of the molding molded at 290 ° C. was 4.2% at 4 mm thickness and 7.5% at 5 mm thickness. The acetaldehyde content of the endplate-shaped molding obtained by molding PET at 275 ° C was 8 ppm.

Example 3

Instead of supplying 0.46 parts by weight of 85% phosphoric acid to the second reactor, PET was prepared in the same manner as in Example 1 except that 0.10 parts by weight of 85% phosphoric acid and 0.24 parts by weight of cobalt acetate tetrahydrate were supplied.

Intrinsic viscosity measured at 25 degreeC in o-chlorophenol of obtained PET (liquid polycondensation product) was 0.65 dl / g, and diethylene glycol unit content was 0.99 weight%.

Thereafter, PET (liquid polycondensation product) was subjected to solid phase polycondensation in the same manner as in Example 1. In o-chlorophenol of obtained PET, the intrinsic viscosity measured at 25 degreeC was 0.88 dl / g, the density was 1.40 g / cm <^3> , and diethylene glycol unit content was 1.01 weight%.

From this PET, two end plate-shaped molded articles were molded in the same manner as in Example 1. The haze of the moldings molded at 290 ° C. was 3.9% at 4 mm thick and 6.9% at 5 mm thick. The acetaldehyde content of the end plate-shaped molding obtained by molding PET at 275 ° C was 9 ppm.

Example 4

PET was prepared in the same manner as in Example 1 except that the amount of antimony trioxide was changed to 4.46 parts by weight and 0.24 parts by weight of trimethylphosphate was used instead of 85% phosphoric acid.

Intrinsic viscosity measured at 25 degreeC in o-chlorophenol of obtained PET (liquid polycondensation product) was 0.64 dl / g, and diethylene glycol unit content was 1.02 weight%.

Thereafter, PET (liquid polycondensation product) was subjected to solid phase polycondensation in the same manner as in Example 1. In o-chlorophenol of obtained PET, the intrinsic viscosity measured at 25 degreeC was 0.85 dl / g, the density was 1.40 g / cm <^3> , and diethylene glycol unit content was 1.03 weight%.

From this PET, two end plate-shaped molded articles were molded in the same manner as in Example 1. The haze of the moldings molded at 290 ° C. was 6.0% at 4 mm thick and 13.2% at 5 mm thick. The acetaldehyde content of the endplate-shaped molding obtained by molding PET at 275 ° C was 10 ppm.

Example 5

PET was prepared in the same manner as in Example 3, except that 1,365 parts by weight of high purity terephthalic acid and 72 parts by weight of isophthalic acid were used and the amount of antimony trioxide was changed to 0.39 parts by weight.

Intrinsic viscosity measured at 25 degreeC in o-chlorophenol of obtained PET (liquid polycondensation product) was 0.60 dl / g, and diethylene glycol unit content was 0.92 weight%.

Thereafter, PET (liquid polycondensation product) was subjected to solid phase polycondensation in the same manner as in Example 1. In o-chlorophenol of obtained PET, the intrinsic viscosity measured at 25 degreeC was 0.80 dl / g, the density was 1.40 g / cm <^3> , and the diethylene glycol unit content was 0.92 weight%.

From this PET, two end plate-shaped molded articles were molded in the same manner as in Example 1. The haze of the moldings molded at 290 ° C. was 3.4% at 4 mm thickness and 4.7% at 5 mm thickness. The acetaldehyde content of the endplate-shaped molding obtained by molding PET at 275 ° C was 10 ppm.

Comparative Example 1

PET was prepared in the same manner as in Example 1 except for supplying antimony trioxide to the second reactor instead of the first reactor.

Intrinsic viscosity measured at 25 degreeC in o-chlorophenol of obtained PET (liquid polycondensation product) was 0.57 dl / g, and diethylene glycol unit content was 0.97 weight%.

Thereafter, PET (liquid polycondensation product) was subjected to solid phase polycondensation in the same manner as in Example 1. In o-chlorophenol of obtained PET, the intrinsic viscosity measured at 25 degreeC was 0.80 dl / g, the density was 1.40 g / cm <^3> , and the diethylene glycol unit content was 0.97 weight%.

From this PET, two end plate-shaped molded articles were molded in the same manner as in Example 1. The haze of the moldings molded at 290 ° C. was 9.6% at 4 mm thick and 35.5% at 5 mm thick. The acetaldehyde content of the endplate-shaped molding obtained by molding PET at 275 ° C was 7 ppm.

Comparative Example 2

PET was prepared in the same manner as in Example 2 except that 85% phosphoric acid was not supplied.

Intrinsic viscosity measured at 25 degreeC in o-chlorophenol of obtained PET (liquid polycondensation product) was 0.66 dl / g, and diethylene glycol unit content was 0.95 weight%.

Thereafter, PET (liquid polycondensation product) was subjected to solid phase polycondensation in the same manner as in Example 1. In o-chlorophenol of obtained PET, the intrinsic viscosity measured at 25 degreeC was 0.89 dl / g, the density was 1.40 g / cm <^3> , and the diethylene glycol unit content was 0.96 weight%.

From this PET, two end plate-shaped molded articles were molded in the same manner as in Example 1. The haze of the moldings molded at 290 ° C. was 4.4% at 4 mm thickness and 8.1% at 5 mm thickness. The acetaldehyde content of the endplate-shaped molding obtained by molding PET at 275 ° C was 14 ppm.

Comparative Example 3

PET was prepared in the same manner as in Example 2 except that 85% phosphoric acid was supplied to the first reactor instead of the second reactor.

Intrinsic viscosity measured at 25 degreeC in o-chlorophenol of obtained PET (liquid polycondensation product) was 0.56 dl / g, and diethylene glycol unit content was 0.92 weight%.

Thereafter, PET (liquid polycondensation product) was subjected to solid phase polycondensation in the same manner as in Example 1. In o-chlorophenol of obtained PET, the intrinsic viscosity measured at 25 degreeC was 0.80 dl / g, the density was 1.40 g / cm <^3> , and the diethylene glycol unit content was 0.95 weight%.

From this PET, the end plate-shaped molded product was molded in the same manner as in Example 1. The haze of the molding molded at 290 ° C. was 10.1% at 4 mm thickness and 37.2% at 5 mm thickness. The acetaldehyde content of the endplate-shaped molding obtained by molding PET at 275 ° C was 10 ppm.

According to the production method of the present invention, the antimony compound as the polycondensation catalyst is not dissolved in ethylene glycol beforehand, but mixed with terephthalic acid and ethylene glycol in an esterification bath in a slurry state. Therefore, no special melting bath is required, so that the number of processes and the simplification of the apparatus can be achieved, and as a result, the cost can be reduced. There is also no need to heat or maintain ethylene glycol at high temperature in order to dissolve the antimony compound in ethylene glycol. Therefore, ethylene glycol hardly degrades, and the amount of diethylene glycol produced is also reduced.

Moreover, since the slurry containing an antimony compound is supplied to a 1st esterification tank among a some esterification tank, the foreign material contamination and transparency fall caused by the introduction of the antimony compound which is not dissolved in a polycondensation process do not arise.

Furthermore, since an antimony compound is added to the 1st step of an esterification process, and a phosphorus compound is added to the 2nd or subsequent esterification step of an esterification process, precipitation of antimony metal is suppressed and it manufactures from the obtained polyethylene terephthalate. Excellent color and transparency of co-current.

Since the polyethylene terephthalate produced by the production method of the present invention is excellent in color and transparency, bottled bottles such as wine, sake, soju, soy sauce, Worcester sauce, seasonings such as miso, carbonated drinks, It can be suitably used for bottled water applications, such as mineral water, juice, green tea, coffee, and black tea.

1 is a schematic diagram illustrating an embodiment of a polyethylene terephthalate production method according to the present invention.

1. Mixer

2. Esterification Bath

3. Liquid polycondensation reaction device

4. Extruder

5. Solid phase polycondensation reaction device

Claims (7)

Using the polyester production apparatus provided with the esterification apparatus which consists of several continuous esterification tank, the liquid-phase polycondensation reaction apparatus, and the solid state polycondensation reaction apparatus as needed, Feeding a slurry containing terephthalic acid, ethylene glycol and an antimony compound to the first esterification tank, A process for producing polyethylene terephthalate characterized by adding a phosphorus compound and at least one compound selected from cobalt compounds, magnesium compounds and manganese compounds as necessary to the second or subsequent esterification bath. The method of claim 1, wherein the antimony compound is antimony trioxide. The method for producing polyethylene terephthalate according to claim 1 or 2, wherein the slurry contains an antimony compound in an amount of 150 to 400 ppm relative to terephthalic acid. The method for producing polyethylene terephthalate according to claim 1 or 2, wherein a slurry containing terephthalic acid, ethylene glycol and an antimony compound is produced at a temperature of 0 to 50 ° C. The method for producing polyethylene terephthalate according to claim 1 or 2, wherein the reaction temperature of the first esterification tank is 240 to 270 ° C. The process for producing polyethylene terephthalate according to claim 1 or 2, wherein the phosphorus compound, the cobalt compound and the antimony compound are added in the form of an aqueous solution. The method for producing polyethylene terephthalate according to claim 1 or 2, wherein isophthalic acid is used in an amount of 1 to 3% based on the total dicarboxylic acid in addition to the terephthalic acid as the dicarboxylic acid component.

Images