JPH11302366A - Production of polyethylene terephthalate and apparatus for the production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently and economically produce a polyester for molding bottles good in quality with the minimum energy by using reactors in an esterification step, a prepolymerization step and the final polymerization step. SOLUTION: A first reactor for reacting an aromatic dicarboxylic acid or its derivative with glycols and producing an oligoester or a polyester having 3-7 average degree of polymerization, a second reactor for carrying out a polycondensation of the resultant product and producing a low polymer having 20-40 average degree of polymerization and a third reactor for further performing the polycondensation of the low polymer to 90-180 average degree of polymerization and producing a high-molecular weight polyester are used and at least one or more of the reactors in the first and the second reactors are composed so as not to have stirring functions with an external power source. Thereby, the polyester for molding bottles is produced. The temperatures in the reactors are preferably 240-295 deg.C in the first reactor, 250-295 deg.C in the second reactor and 270-295 deg.C in the third reactor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for continuously producing polyester-based polymers such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a polycondensation polymer such as polyethylene terephthalate, terephthalic acid and ethylene glycol as raw materials are put into a mixing tank at an appropriate ratio for esterification and esterified by a pump. Send to reaction tank. In this esterification step, two or three stirring tanks with stirring blades are arranged in series, and water produced as a by-product is separated by a distillation column. Next, a plurality of vertical stirring tanks and horizontal stirring tanks are installed as a pre-polymerization step, and a horizontal stirring tank is installed as a final polymerization step. A condenser is installed in the tank for these polymerization steps to remove ethylene glycol as a by-product, and the vessel is operated in a reduced pressure atmosphere. In the conventional polyester production process, the number of reaction vessels is 4 to 6 cans, each reaction vessel is equipped with a stirring blade and its power source, and a distillation column and a condenser for separating and removing by-products are installed. ing. Further, since the polymerization process is operated in a reduced-pressure atmosphere, the vacuum means must be operated by another apparatus, and the operation of the production apparatus requires high maintenance costs and equipment costs.

[0003]

SUMMARY OF THE INVENTION The problem of the present invention is an improvement over known processes for the production of high molecular weight polyesters, which increases the efficiency of the entire apparatus and saves energy in plant equipment, thereby operating economically. Is what you do.

An object of the present invention is to improve the above prior art,
An object of the present invention is to provide a continuous polycondensation apparatus and a continuous polycondensation method for efficiently reacting a high quality polymer for a bottle with minimum energy by using a minimum necessary reactor configuration.

[0005]

The object of the present invention is to provide an esterification step, a pre-polymerization step, and a final polymerization step as one tank,
A vessel requiring stirring power is achieved by only the final polymerization step.

[0006]

FIG. 1 shows an embodiment of the present invention.
FIG. 1 is an apparatus training diagram of a continuous production process of polyethylene terephthalate according to the present invention. As the industrial polyester production method, the direct esterification method is very economically advantageous, and thus the direct esterification method has recently been widely used. In FIG. 1, reference numeral 1 denotes a raw material adjusting tank for mixing and stirring a predetermined ratio of TPA (terephthalic acid) and EG (ethylene glycol), which are raw materials for polyethylene terephthalate. During the production process, additives such as a polymerization reaction catalyst, a stabilizer, and a color tone adjuster may be added at this stage. In addition, in the case of a combination of a catalyst and a stabilizer, it may be introduced after the esterification step is completed by an intermediate addition device described later. Examples of the polymerization reaction catalyst include metal compounds such as antimony, titanium, germanium, tin, and zinc.Depending on the type and combination of the catalysts used, not only the reaction rate differs, but also the hue and thermal stability of the resulting polyester. It is well known that they are different. Furthermore, these reactions are carried out at a high temperature for a long time in the presence of a catalyst, and are accompanied by various side reactions, and the polymer is colored yellow, and the content of diethylene glycol (DEG) and the terminal carboxyl group concentration are more than appropriate values. And physical properties such as a decrease in the melting point and strength of the polyester are reduced.
Attempts have been made to develop new catalysts in order to solve such problems, but antimony compounds which are currently most industrially used, especially antimony triacid, are excellent in price and performance. However, even if this catalyst is used, coloring of the produced polyester polymer cannot be avoided. For this reason, phosphorus stabilizers (for example, trimethyl phosphate, triphenyl phosphate) have been used in combination as stabilizers for improvement. In another manufacturing process, the quality is stabilized by devising a position where a polymerization catalyst and a stabilizer are charged. In a typical process, it is preferable to use 200 to 400 ppm of the catalyst and 50 to 200 ppm of the stabilizer. The raw material adjusted as described above is supplied to the esterification reaction tank 3
Via the supply line 2 that supplies the raw material to the vessel. The outer periphery of the esterification reaction tank (first reactor) 3 has a jacket structure (not shown) for keeping the processing liquid at the reaction temperature. Exchange 4
Is provided to heat the treatment liquid by an external heat source, and to proceed the reaction while circulating the internal liquid by natural circulation.
Here, the most desirable type of reactor is a calandria type in which the processing solution in the reactor is naturally circulated by utilizing the evaporating action of a by-product produced by the self-reaction of the esterification reaction. Since this type of reactor does not require an external stirring power source, there is an advantage that the apparatus configuration is simple, the shaft sealing device for the stirring shaft is not required, and the production cost of the reactor is low. As an example of such a reactor, an apparatus as disclosed in Japanese Patent Application No. 8-249969 is desirable. However, the present invention is not limited to this apparatus, and a reactor having a stirring blade may be used for process reasons. In the first reactor, water generated by the reaction becomes water vapor, and forms a vapor phase section 5 with the vaporized EG vapor. At this time, as the recommended reaction conditions, the temperature is preferably 240 to 280 degrees, and the pressurization condition is desirable. The gas in the gas phase 5 is separated into water and EG by a rectification tower (not shown) provided on the upstream side, the water is removed outside the system, and the EG is returned to the system again.
As an advantage of the present invention, it is possible to reduce the number of rectification towers by treating the esterification step in one reactor, and not only the production cost of the rectification tower but also the control of the number of pipes and valves. The number and the like can be reduced, resulting in a significant reduction in equipment cost. The treatment liquid after a predetermined reaction time in the esterification reaction tank 3 reaches a predetermined esterification rate, and is supplied to the initial polymerization tank (second reactor) 7 through the communication pipe 6. The connecting pipe 6 may be provided with a midway addition device 16. This apparatus is for introducing a polymerization catalyst, a stabilizer, an additive, etc., which do not contribute to the esterification reaction, into the process, and a plurality of such apparatuses are provided according to the type of the input material. Furthermore, a static mixer or a line mixer may be attached to improve the dispersibility in the process liquid after the addition. After this,
The treatment liquid is heated to a predetermined reaction temperature by the heat exchanger 8 to perform a polycondensation reaction to increase the degree of polymerization. At this time, the reaction conditions are from 270 to 295 degrees, the pressure is from 266 to 133 Pa, and the degree of polymerization is from about 20 to 40. Although the initial polymerization tank shown in this example is described using a reactor having no stirring blade, this reactor is not limited. However, in the initial polymerization stage, the reaction is a stage in which the polymerization reaction rate is governed by the reaction speed, and the reaction proceeds smoothly if a sufficient amount of heat required for the reaction is supplied. From this viewpoint, the processing liquid does not need to be subjected to unnecessary stirring action by the stirring blade, and EG generated by the polycondensation reaction is not required.
Only has to leave the system. As an optimum reactor for such an operation, an apparatus as shown in Japanese Patent Application No. 8-233855 is desirable. The EG generated by the reaction is vaporized in the gas phase section 9 kept in a reduced pressure atmosphere, condensed by a condenser provided on the upstream side thereof, and then discharged out of the system. As an advantage of the present invention, it is possible to reduce the number of condensers to one by treating the initial polymerization step in one reactor,
Not only the production cost of the condenser but also the number of pipes and valves and the number of control devices can be reduced, resulting in a significant reduction in equipment costs. After a predetermined reaction time has passed in the initial polymerization tank (second reactor) 7, the processing liquid is supplied to the final polymerization machine (third reactor) 11 through the communication pipe 10. In the final polymerization machine, the polycondensation reaction is further promoted while undergoing a good surface renewing action by the stirring blade 12 having no stirring shaft at the center to increase the degree of polymerization to produce a polymer having a desired degree of polymerization. The most suitable apparatus for the final polymerization machine (third reactor) is described in Japanese Patent Application No.
The device described in 33857 is the most excellent in surface renewal performance and power consumption characteristics. Further, since the viscosity range of the processing liquid is wide, the processing which has been conventionally performed by dividing the processing liquid into two tanks can be performed by one apparatus, and the cost of the apparatus can be greatly reduced.

In the following, embodiments of the present invention will be described. In a slurry tank adjusted so that the molar ratio of ethylene glycol to high-purity terephthalic acid is 1.7, 300 ppm of antimony triacid is used as a polymerization catalyst, and trimethyl is used as a stabilizer. Phosphoric acid was added at 100 ppm, and the operation was performed at a throughput of 80 kg / h. At this time, the operating conditions of each reactor were as follows: esterification reaction temperature 285 ° C., pressure 50 kPa, residence time 2 hours, reaction temperature 288 ° C. of initial polymerization second reactor, pressure 2.4 kPa, residence time 1 hour, final polymerization Reaction temperature of the third reactor at 282 ° C., pressure 0.13 kPa, residence time 1
It was time. The intrinsic viscosity of the produced polymer is 0.63
(Dl / g), the acid value is 33 (equivalent / ton), and the hue is a polymer chip manufactured by Nippon Denshoku Industries Co., Ltd.
As a result of measurement by E-2000, L = 58.6, b =
1.74 was obtained. The result is of the same quality as the polymer produced by the conventional five-can process.

When polyethylene terephthalate for a bottle is manufactured in the above-described apparatus configuration, the cost of the apparatus can be saved because the number of reactors is reduced as compared with the conventional apparatus configuration. Since the number of distillation towers and condensers attached to the equipment is reduced, piping, instrumentation parts and valves connecting them can be greatly saved, and utility costs such as vacuum sources and heat transfer equipment are greatly reduced, so running costs are reduced. Has the advantage of being cheaper.

[0009]

According to the present invention, the efficiency of the whole apparatus is improved by using three reactors for the continuous production of polyester for bottles, namely, an esterification step, a prepolymerization step and a final polymerization step. It operates economically with energy savings in the equipment.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram of a continuous production process of polyethylene terephthalate showing one embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Raw material adjustment tank, 2 ... Raw material supply line, 3 ... Esterification reaction tank, 4 ... Heat exchanger, 5 ... Gas phase part, 6 ... Connecting pipe, 7 ...
Initial polymerization tank, 8 heat exchanger, 9 gas phase section, 10 connecting pipe, 11 final polymerization machine, 12 stirring blade, 13 polymer, 14 stirring power source, 15 midway addition charging line, 1
6 ... midway addition device.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hiroo Suzuki 794, Higashi-Toyoi, Kazamatsu, Kudamatsu, Yamaguchi Prefecture Inside the Kasado Plant of Hitachi, Ltd. Inside the Kasado Plant of Hitachi, Ltd.

Claims (6)

[Claims] 1. A first reactor for producing an oligoester or polyester having an average degree of polymerization of 3 to 7 or less by reacting an aromatic dicarboxylic acid or a derivative thereof with a glycol, and polycondensing the product. , Average degree of polymerization 20 to 4
And a third reactor for producing a high-molecular-weight polyester by further polycondensing the low-polymer and producing a high-molecular-weight polyester by polycondensing the average polymerization degree from 90 to 180. At least one of the first reactor and the second reactor is configured so as not to have a stirring function by an external power source, and a polyester for bottle molding is manufactured. . 2. The process for continuous production of polyester according to claim 1, wherein the third reactor has an inlet and an outlet for the liquid to be treated at one lower end and the lower end in the longitudinal direction of the main body of the horizontal cylindrical container, respectively. Has a volatile outlet at the top of the body,
A device provided with a stirring rotor that rotates close to the inside of the main body in the longitudinal direction inside the main body, wherein the stirring rotor inside the main body is composed of a plurality of stirring blade blocks according to the viscosity of the processing liquid, and the center of the stirring rotor is A continuous method for producing a polyester, comprising producing a polyester for bottle molding using a production apparatus comprising a reactor having a stirring blade having no rotating shaft in a part. 3. The method for continuously producing a polyester according to claim 1, wherein the molar ratio of the aromatic dicarboxylic acid or a derivative thereof to the glycol is 1: 1.05 to 1: 1.
2.0, and the temperature of the first reactor is 240
Degrees to 295 degrees, the pressure is 3 × 10 ⁵ Pa from atmospheric pressure, the temperature of the second reactor is 250 to 295 degrees, the pressure is 133 Pa from atmospheric pressure, and the temperature of the third reactor is 270 degrees to 2
A continuous method for producing polyester, comprising producing polyester for bottle molding by operating at 95 degrees and a pressure in the range of 200 to 13.3 Pa. 4. The method for continuous production of polyester according to claim 1, 2 or 3, wherein the rotation speed range of the stirring blade of the third reactor is 0.5 rpm to 10 rpm to produce polyester for bottle molding. A continuous method for producing polyester. 5. The continuous production method of a polyester according to claim 1, 2 or 3, wherein the total reaction time of said first reactor, second reactor and third reactor is operated between 3 and 8 hours. And producing a polyester for bottle molding. 6. A first reactor for producing an oligoester or polyester having an average degree of polymerization of 3 to 7 or less by reacting an aromatic dicarboxylic acid or a derivative thereof with a glycol, and polycondensing the product. , Average degree of polymerization 20 to 4
And a third reactor for producing a high molecular weight polyester by subjecting the low polymer to polycondensation further and polycondensing from an average degree of polymerization of 90 to 180 to produce a high molecular weight polyester. At least one of the first and second reactors is configured so as not to have a stirring function by an external power source, and manufactures polyester for bottle molding. .