JPH11335453A - Production of poly(ethylene terethalate) and manufacturing equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To continuously produce high-quality polyester for fibers with minimum energy by specifying at least one selected from the first reactor and the second reactor in the production of polyester by the reaction of aromatic dicarboxylic acids and glycols via three reactors. SOLUTION: In the first reactor (the esterification vessel) 3, an aromatic dicarboxylic acid (or its derivative) is allowed to react with a glycol to form oligoesters with an average polymerization degree of 3-7 or polyester. Then, in the second reactor (the initial polymerization vessel) 7, the esterified product is subjected to the polycondensation reaction to form a low polymer with an average polymerization degree of 20-40. Finally, in the third reactor (the final polymerization vessel), the low polymer is further subjected to the polycondensation reaction to produce a high polymer with an average polymerization degree of 90-180. In this case, at least one selected from the first reactor 3 and the second reactor 7 is unequipped with an agitation mechanism driven by an external power source and the polyester is produced continuously.

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. As a related art of this kind, there is WO95 / 11268.

[0003]

SUMMARY OF THE INVENTION 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 operates economically with energy savings in factory equipment. It is.

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 fibers 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 of 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 passes through a supply line 2 that supplies the raw material to an esterification reaction tank 3. 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. An exchanger 4 is provided to heat the processing liquid by a heat source from the outside, 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, Japanese Patent Application No. Hei 8-2
An apparatus such as that shown in US Pat. 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 mixed with water and E by a rectification tower (not shown) provided on the upstream side.
G, water is removed outside the system, and 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.

[0008] The processing solution having passed 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 equipment is used for polymerization catalysts and stabilizers that do not contribute to the esterification reaction,
This is for introducing additives and the like into the process, and a plurality of such devices are installed according to the type of the input material. In particular, for fiber use, titanium dioxide dispersed in an ethylene glycol solution for color tone adjustment is injected from the intermediate addition line 15 through the intermediate addition device 16. At this time, the temperature of the processing liquid in the communication pipe 6 is set to the minimum allowable temperature of the process line (recommended temperature is 260 ° C. to 270 ° C.), and the pressure of the line is set to be higher than the vapor pressure of the added ethylene glycol. Even in the temperature control of the heat medium in the whole plant, the temperature of the line of the connecting pipe 6 can be controlled particularly. Further, a static mixer or a line mixer may be attached in order to improve dispersibility in the process liquid after the addition. Thereafter, 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 embodiment is described using a reactor having no stirring blade, the present invention is not limited to this reactor. 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 only needs to be released from 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 by processing the initial polymerization process in one reactor, thereby reducing not only the production cost of the condenser but also the number of piping and valves and the number of control devices. As a result, the cost of the apparatus is greatly reduced. 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. Final polymerization machine (3rd
As the most suitable apparatus as the reactor, the apparatus described in Japanese Patent Application No. 8-233857 has the best 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, an embodiment 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, 200 ppm of antimony triacid is used as a polymerization catalyst, and trimethyl is used as a stabilizer. Phosphoric acid 50 ppm, titanium dioxide 35
The operation was carried out at a treatment amount of 80 kg / h with the input of 00 ppm. At this time, the operating conditions of each reactor were as follows: esterification reaction temperature 280 ° C., pressure 50 kPa, residence time 2 hours, reaction temperature 288 ° C. of initial polymerization second reactor, pressure 2.4 kP.
a, residence time: 1 hour, reaction temperature of the third reactor for final polymerization: 280 ° C., pressure: 0.13 kPa, residence time: 0.9 to 1.1 hours. The intrinsic viscosity of the produced polymer is 0.57 to 0.63 (dl / g), and the acid value is 33 to 3
0 (equivalent / ton), and the hue was measured using a Hunter method on a polymer chip with SE-2000 manufactured by Nippon Denshoku Industries Co., Ltd., and as a result, L = 75.9 to 77.5 and b = 1.83 to 1.21. I got The result is of the same quality as the polymer produced by the conventional five-can process.

When polyethylene terephthalate for fibers 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.

[0012]

According to the present invention, the efficiency of the whole apparatus can be improved by using three reactors for continuous production of polyester for fiber, namely, an esterification step, a prepolymerization step, and a final polymerization step. It can be operated economically by saving energy of equipment.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram showing an embodiment of a continuous production process of polyethylene terephthalate according to 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 (8)

[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, Average degree of polymerization 20 to 40
A polyester is produced by using a second reactor for producing a low-polymerized product of the above, and a third reactor for further polycondensing the low-polymerized product and polycondensing from an average degree of polymerization of 90 to 180 to produce a high-molecular-weight polyester. In the method, at least one or more of the first and second reactors is used to manufacture a polyester for fiber using a manufacturing apparatus including a reactor having no stirring function by an external power source. A continuous method for producing polyester. 2. The third reactor according to claim 1, wherein the reactor has an inlet and an outlet for the liquid to be treated at one lower end and the lower end at the other end in the longitudinal direction of the horizontal cylindrical container main body, respectively. A stirring rotor that has a volatile material outlet and rotates in the longitudinal direction inside the main body and close to the inside of the main body, and the stirring rotor inside the main body has a plurality of stirring blade blocks according to the viscosity of the processing liquid. And producing a polyester for fibers using a production apparatus comprising a reactor having a stirring blade without a rotating shaft at the center of a stirring rotor. 3. 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, Average degree of polymerization 20 to 40
A polyester is produced by using a second reactor for producing a low-polymerized product of the above, and a third reactor for further polycondensing the low-polymerized product and polycondensing from an average degree of polymerization of 90 to 180 to produce a high-molecular-weight polyester. In the method, the third reactor has an inlet and an outlet for the liquid to be treated at one lower end and the lower end at the other end in the longitudinal direction of the horizontal cylindrical container body, has an outlet for volatiles at the upper part of the main body, A device equipped with a stirring rotor that rotates close to the inside of the main body in the longitudinal direction, and 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 rotates at the center of the stirring rotor. A continuous method for producing polyester, comprising producing a polyester for fibers using a production apparatus comprising a reactor having stirring blades without a shaft. 4. The continuous production method of a polyester according to any one of claims 1, 2 and 3, wherein the molar ratio of the aromatic dicarboxylic acid or its derivative as a raw material to the glycols is 1: 1.05-1. : Supplied in the range of 2.0,
The temperature of the reactor is 240 to 295 degrees, the pressure is 3 × 10 ⁵ Pa from the atmospheric pressure, and the temperature of the second reactor is 250 to 295.
Degree, pressure is from atmospheric pressure to 133 Pa, the temperature of the third reactor is in the range of 270 to 295 degrees, and the pressure is in the range of 200 to 13.3 Pa to produce polyester for fibers. Production method. 5. The polyester for fiber production according to claim 1, wherein the rotation speed of the stirring blade of the third reactor is 0.5 rpm to 10 rpm. A continuous method for producing polyester. 6. The continuous production method of a polyester according to claim 1, wherein the total reaction time of the first reactor, the second reactor and the third reactor is between 3 and 8 hours. A continuous production method of polyester, characterized by producing a polyester for fibers by operating the apparatus. 7. The continuous production method of a polyester according to claim 4, wherein when adding ethylene glycol in which titanium dioxide is dispersed to a pipe between the first reactor and the second reactor, a process temperature of a line to be added is added. A continuous process for producing polyester for fibers, wherein the process temperature is set to the minimum temperature of the whole process, the process pressure is controlled to be higher than the vapor pressure of ethylene glycol, and the process is operated to produce polyester for fibers. 8. 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, Average degree of polymerization 20 to 40
A second reactor for producing a low polymer of the above, and a third reactor for further polycondensing the low polymer and polycondensing from an average degree of polymerization of 90 to 180 to produce a high molecular weight polyester for fibers, An apparatus for continuously producing polyester, wherein at least one or more of the first and second reactors is a reactor having no stirring function by an external power source.