JP2000344874A - Method and apparatus for producing polybutylene terephthalate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a polyester with a minimum necessary reactor combination and with minimum energy by reacting terephthalic acid with 1,4-butanediol in a first reactor, polycondensing the resultant oligomer in a second reactor, and polycondensing the resultant low polymer in a third reactor to give a high polymer. SOLUTION: An aromatic dicarboxylic acid (derivative) component mainly comprising terephthalic acid is reacted with a glycol component mainly comprising 1,4-butanediol in a first reactor comprising a first esterification vessel 3 and a second esterification vessel 10 connected in series; the resultant oligomer having an average degree of polymerization of 3-7 is polycondensed in an initial polymerization vessel 14, which is a second reactor; and thus formed low polymer having an average degree of polymerization of 20-40 is polycondensed in a final polymerization vessel, which is a third reactor, giving polybutylene terephthalate having an average degree of polymerization of 70-180.

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 polybutylene terephthalate and polyethylene terephthalate.

[0002]

2. Description of the Related Art Polybutylene terephthalate (hereinafter referred to as PB)
Resins have excellent crystallization properties and excellent mechanical properties, electrical properties, heat resistance, etc., and have recently been applied to electrical, electronic, mechanical, and automotive applications, and demand has steadily increased. I have.

The following method is considered as a method for manufacturing PBT. As raw materials, a dialkyl terephthalate ester containing dimethyl terephthalate as a main component and a glycol containing 1,4-butanediol (hereinafter referred to as BD) as a main component are put into a mixing tank at an appropriate ratio, and a transesterification catalyst is added and adjusted. After that, the mixture is sent to a transesterification reaction tank set at a predetermined reaction temperature by a pump. In this transesterification reaction, two or three stirring tanks with stirring blades are arranged in series, and methanol, which is a by-product, tetrahydrofuran (hereinafter referred to as THF) generated by the decomposition of BD and water are mixed in a distillation column. To separate. Next, a polymerization catalyst is added and the process proceeds to a polymerization reaction step. First, 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. Condensers are installed in the tanks of these polymerization steps to remove BD, THF, and water that are produced as by-products, and are operated in a reduced pressure atmosphere. In a conventional PBT continuous production process, the number of reactors is four to six, each reactor 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. is set up. Further, since the polymerization step 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. A related technique of this kind is described in Japanese Patent Application Laid-Open No. 51-37187.

[0004]

Hitherto, a production method for industrially producing a large amount of high molecular weight polyester, especially PBT, has not been established, and more economical from the viewpoint of the efficiency of the whole apparatus and the energy saving of the factory equipment. Facilities and operating methods have not been established.

An object of the present invention is to provide a method and an apparatus for producing polybutylene terephthalate, which can more efficiently mass-produce polybutylene terephthalate.

Another object of the present invention is to provide a method and apparatus for producing polybutylene terephthalate, which efficiently reacts a high-quality polymer with minimum energy by using a minimum necessary reactor configuration.

[0007]

The object of the present invention is to use terephthalic acid (hereinafter referred to as TPA) and BD as raw materials for PBT production, and to carry out direct esterification reaction step and polymerization reaction step in separate reactors. It is achieved by doing. Further, two to four reactors may be provided, and the reactors may be shared depending on the viscosity.

[0008]

FIG. 1 shows an embodiment of the present invention.
FIG. 1 is an apparatus training diagram of a PBT continuous manufacturing process according to the present invention. As an industrial polyester production method, the direct esterification method is very economically advantageous. In FIG. 1, reference numeral 1 denotes a raw material adjusting tank for mixing and stirring TPA and BD, which are raw materials of PBT, at a predetermined ratio. During the production process, additives such as a polymerization reaction catalyst, a stabilizer, and a quality control agent may be added at this stage. Examples of polymerization catalysts include metal compounds such as organic titanium, organic tin, and organic zirconia. Depending on the type and combination of catalysts used, not only the reaction rate differs, but also the quality of the resulting PBT, such as hue and thermal stability. Has a great effect on Furthermore, these reactions are carried out at a high temperature for a long time in the presence of a catalyst, so that various side reactions are involved, and the polymer is colored, and the content of THF and the concentration of terminal carboxyl groups are increased to appropriate values. P
Physical properties such as quality deterioration and strength of the BT are deteriorated. Currently, the most industrially used organic titanium is excellent in price and performance. However, even if this catalyst is used, coloring of the produced polyester polymer cannot be avoided. For this purpose, a phosphorus-based stabilizer (for example,
Phosphoric acid, trimethyl phosphate, triphenyl phosphate, etc.). In addition, in order to stabilize the quality, it is conceivable to devise the position where the polymerization catalyst and the stabilizer are charged. In a usual process, the amount of the catalyst is preferably 20 to 85 ppm in terms of the concentration of titanium metal, and the amount of the stabilizer is preferably 0 to 600 ppm in the concentration of the P metal, if necessary. The raw material adjusted as described above goes through the supply line 2 that supplies the raw material to the first esterification reaction tank 3. The outer periphery of the first esterification reaction tank (first reactor) 3 has a jacket structure (not shown) for keeping the processing liquid at the reaction temperature. A heat exchanger 4 is provided to heat the processing liquid by a heat source from the outside, and the reaction proceeds 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-
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 steam, and forms a gas phase portion 5 together with the vaporized BD vapor and THF vapor. The recommended reaction conditions at this time are preferably a temperature of 220 to 275 ° C. and a pressurized condition. The gas in the gas phase 5 is separated into water, THF and BD by a distillation column (not shown) provided on the upper side thereof,
The water and the THF are removed outside the system, and the BD is returned to the system again through a purification step and the like. The processing solution that has reached a predetermined esterification reaction rate in the first esterification reaction tank 3 is supplied to the second esterification reaction tank (second reactor) 10 via the communication pipe 6. A control valve 7 for adjusting the flow rate of the processing liquid is provided in the middle of the communication pipe 6. With this valve, the liquid level in the first reactor is controlled to be constant, and the reaction time is kept constant. Second reactor 1
At 0, a coil type heat exchanger 13 is installed as a heating means for the liquid inside the liquid, and a jacket structure (not shown) is provided on the outer periphery to maintain the reaction temperature. It has equipment 8 to improve the heat transfer efficiency of the processing liquid and to perform the mixing action. The second reactor is equipped with a facility (not shown) capable of adding and adding a polymerization catalyst and adding an additive as needed (not shown). The liquid is further reacted to a target esterification rate. The gas component generated by the reaction is the first
A gas phase portion 9 is formed in the same manner as in the reactor, and is separated into water, THF and BD by a distillation column provided on the upper side thereof, and is taken out of the system. As the reaction conditions to be recommended at this time, it is preferable that the temperature is 220 to 275 ° C. and the pressure is slightly lower than that of the first reactor. By constituting the esterification reaction step with two reaction vessels, it is possible to shorten the reaction time as compared with the case of one reactor. The first reactor is set to maximize the performance of the reactor, and the second reactor is used to prevent the reduction of the reaction rate at a high esterification rate by adding BD if necessary. are doing. The esterification ratio of the first reactor and the second reactor is set to an optimum condition that minimizes the total reaction time of both according to the performance of the reactor used. The treatment liquid after a predetermined reaction time in the first esterification reaction tank 3 and the second esterification reaction tank 10 reaches a predetermined esterification rate, and is treated by an oligomer pump 12 provided in the middle of a communication pipe 11 by an initial polymerization tank ( (Third reactor) 14. This oligomer pump controls the liquid level in the second reactor to be constant, keeps the reaction time constant, and makes the quality of the oligomer uniform. The treatment liquid supplied to the initial polymerization tank is heated to a predetermined reaction temperature by the heat exchanger 15 to perform a polycondensation reaction to increase the degree of polymerization. At this time, the reaction conditions are 220 to 280 degrees and the pressure is 266.
The reaction is carried out from Pa to 133 Pa to a degree of polymerization of 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 point of view, the treatment liquid does not need to be subjected to unnecessary stirring action by the stirring blade, and it is sufficient that the BD generated by the polycondensation reaction is separated out of the system. As an optimal reactor for such an operation, an apparatus as shown in Japanese Patent Application No. 8-233855 is desirable. BD and water generated by the reaction and T
The HF is vaporized in the gas phase 16 maintained 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. Initial polymerization tank (third reactor)
The processing solution having passed a predetermined reaction time in 14 is supplied to a final polymerization machine (fourth reactor) 18 through a communication pipe 17. In the final polymerization machine, the polycondensation reaction is further promoted while undergoing a good surface renewing action by the stirring blade 19 having no stirring shaft at the center to increase the degree of polymerization to produce a polymer having the desired degree of polymerization. As an apparatus most suitable as a final polymerization machine (fourth reactor), an apparatus described in Japanese Patent Application No. 8-233857 is the most excellent in surface renewal performance and power consumption characteristics. Since this apparatus has a wide viscosity range of the processing liquid, the processing which has conventionally been 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. From the viewpoint of quality, the residence time of the entire polymerization step is in an optimal range of 2 to 4 hours. Also, the residence time can be lengthened by adjusting the temperature and pressure as necessary, for example, when reducing the production volume,
May be implemented to keep quality fluctuations to a minimum.

In the above-described apparatus configuration, when PBT is continuously manufactured, the number of reactors is reduced as compared with the apparatus configuration conventionally considered, so that the manufacturing cost of the apparatus can be reduced and the number of apparatuses is reduced. Since the number of distillation towers and condensers attached to the equipment is reduced, the piping, instrumentation parts, valves, etc. connecting them can be greatly saved, and the utility-related costs such as vacuum sources and heat transfer equipment are greatly reduced, so running costs are reduced. There is an advantage that can be cheap.

Test Examples Hereinafter, the present invention will be specifically described with reference to test examples. The intrinsic viscosity of the test example is a value calculated from a measurement result at a measurement temperature of 30 ° C. using an Ostwald viscometer using 50 wt% of phenol and 50 wt% of tetrachloroethane as a solvent. The acid value is determined at 230 ° C., 5 using benzyl alcohol as a solvent.
It is a value measured by heating and dissolving for 1 minute and performing neutralization titration. The color was measured by a color difference meter SE-2000 manufactured by Nippon Denshoku Industries, and the melting point was measured by Rigaku Thermal Analyzer DSC.
It was measured at a temperature rising rate of 5 ° C./min using −8230. As shown in Table 1, it was produced by continuous operation of the direct esterification method of TPA and BD. Intrinsic viscosity 0.68 to 0.86 dl / g only by melt polymerization,
Acid value is 19 to 27 eq / ton, color b value is 2.1
The following high quality PBT was obtained. The total reaction time at this time was from 6.8 to 9.5 hours, and it was confirmed that polybutylene terephthalate could be continuously produced by the apparatus configuration and reaction conditions of the present invention. .

[0011]

[Table 1]

[0012]

According to the present invention, the continuous esterification process of PBT is directly performed by one or two reactors in the esterification step,
Similarly, by sharing the polymerization step with one reactor or two reactors for the pre-polymerization step and the final polymerization step, the efficiency of the whole apparatus is improved, and the operation can be economically performed by saving energy of the production equipment. is there.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram showing one embodiment of a continuous PBT manufacturing process according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Raw material adjustment tank, 2 ... Raw material supply line, 3 ... 1st esterification reaction tank, 4 ... Heat exchanger, 5 ... Gas phase part, 6 ... Connecting pipe,
7 ... Control valve, 8 ... Stirring equipment, 9 ... Gas phase part, 10 ... Second esterification reaction tank, 11 ... Connection pipe, 12 ... Oligomer pump, 13 ... Heat exchanger, 14 ... Initial polymerization tank, 15 ... Heat Exchanger, 16: gas phase, 17: connecting pipe, 18: final polymerization machine, 19: stirring blade, 20: polymer, 21: stirring power source.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor, Hofumi Maeda 794, Higashi-Toyoi, Kazamatsu, Kamamatsu, Yamaguchi Prefecture Inside the Kasado Works, Hitachi, Ltd. Hitachi Kasado Works (72) Inventor Hiroo Suzuki 794, Higashi-Toyoi, Kazamatsu City, Yamaguchi Prefecture F-term (reference) 4J029 AA03 AB04 AB05 AC01 AC02 AD01 AD02 AD10 BA05 CB06A KB02 KB22 KB25 KC02 KD01 KD02 KD05 KD06 KE05 KE07 KE15 LA05 LA09 LA10 LA14

Claims (7)

[Claims] An aromatic dicarboxylic acid containing terephthalic acid as a main component or a derivative thereof is reacted with a glycol containing 1,4-butanediol as a main component to obtain an average degree of polymerization of 3 or more.
A first step of producing an oligomer of from 7 to 7 in a first reactor, a second step of subjecting the oligomer to polycondensation to produce a low polymer having an average degree of polymerization of 20 to 40 in a second reactor, A third step of further polycondensing the low-polymerized product and polycondensing from an average degree of polymerization of 70 to 180 to produce a high-molecular-weight polyester in a third reactor. 2. A method according to claim 1, wherein said first reactor comprises first and second reaction vessels connected in series. Continuous production method. 3. The continuous production method of polybutylene terephthalate according to claim 2, wherein the starting material is an aromatic dicarboxylic acid containing terephthalic acid as a main component or a derivative thereof, and a glycol containing 1,4-butanediol as a main component. Is supplied to the first reaction tank in a molar ratio of 1: 1.2 to 1: 3.0, and the temperature of the first reaction tank is 220 ° C.
275 degrees, the pressure is 3 × 10 ⁵ Pa from atmospheric pressure,
The temperature of the reaction tank is 220 to 275 degrees, the pressure is 5 × 10 ⁴ Pa from the atmospheric pressure, and the temperature of the second reactor is 220 to 2 degrees.
80 ° C, pressure from atmospheric pressure to 133 Pa, temperature of the third reactor from 220 ° C to 280 ° C, pressure from 200 to 13.
A method for continuously producing polybutylene terephthalate, which is operated in a range of 3 Pa. 4. The continuous production method of polybutylene terephthalate according to claim 1, 2 or 3, wherein the total reaction time from the inlet of the first reactor to the outlet of the third reactor is 4 to 9.5 hours. A continuous process for producing polybutylene terephthalate. 5. The continuous production method of polybutylene terephthalate according to claim 1, 2 or 3, wherein the third reactor is provided at one lower end and at the lower end of the other end in the longitudinal direction of the horizontal cylindrical container body. An apparatus having an inlet and an outlet, having a volatile substance outlet at the upper part of the main body, and having a stirring rotor that rotates in proximity to the inside of the main body in the longitudinal direction inside the main body, wherein the stirring rotor inside the main body is used for processing liquid. It is a reactor that is composed of a plurality of stirring blade blocks according to the viscosity and has stirring blades without a rotating shaft at the center of the stirring rotor,
The rotation speed range of the stirring blade is 0.5 rpm to 10 rpm.
A continuous method for producing polybutylene terephthalate. 6. The method for continuously producing polybutylene terephthalate according to claim 2 or 3, wherein 1
A continuous polybutylene terephthalate characterized by increasing a 1,4-butanediol concentration with respect to an unreacted carboxyl end group concentration by adding a part or all of a polymerization catalyst using -4 butanediol as a solvent or an additive. Production method. 7. An aromatic dicarboxylic acid having terephthalic acid as a main component or a derivative thereof and a glycol having 1,4-butanediol as a main component are reacted to obtain an average degree of polymerization of 3 or more.
A first reactor and a second reactor for producing an oligomer having a molecular weight of 7 or less, a third reactor for producing a low polymer having an average degree of polymerization of 20 to 40 by subjecting the oligomer to polycondensation, Is further polycondensed to give an average degree of polymerization of 70 to 180.
And a fourth reactor for producing a high-molecular-weight polyester by polycondensation to a continuous production apparatus of polybutylene terephthalate.