JPS6058220B2 - Method of supplying slurry of terephthalic acid and ethylene glycol to a reaction vessel - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for supplying a slurry of terephthalic acid and ethylene glycol to an esterification reactor for esterifying terephthalic acid with ethylene glycol.

Traditionally, polyethylene terephthalate, which is useful as a polymer for manufacturing fibers, films, and other molded products, has been produced using dimethyl terephthalate and ethylene glycol as starting materials, but in recent years polyethylene terephthalate has been produced directly from terephthalic acid and ethylene glycol. A direct weight method has been developed to produce .

This method has the advantage of producing inexpensive polymers due to lower raw material costs and superior reactivity compared to conventional methods, as well as the ability to recover and purify methanol generated during the reaction process of conventional methods. It has the advantage of being unnecessary.

However, since terephthalic acid is poorly soluble in ethylene glycol and the esterification reaction product obtained from terephthalic acid and ethylene glycol, the direct weight method is likely to cause a heterogeneous reaction.

As the proportion of insoluble terephthalic acid in the reaction system increases, the reaction mixture becomes lumpy or muddy, and even when heat is applied to the reaction system, the heat transfer effect is poor, making it difficult to maintain a high reaction temperature. It will be disadvantageous. Conversely, if the ratio of terephthalic acid is decreased and the ratio of ethylene glycol is increased, the by-product of diethylene glycol will increase and the quality of the resulting polymer will deteriorate. Therefore, we developed a method of lowering the solid phase ratio in the reaction system while keeping the ratio of ethylene glycol to terephthalic acid low. In other words, terephthalic acid and ethylene glycol, which have a high ratio of terephthalic acid, are continuously supplied to the esterification reactor. However, methods have been proposed to maintain a relatively high esterification reaction rate and suppress heterogeneity of the reaction system.

This method also has a certain effect, but when feeding the slurry of terephthalic acid and ethylene glycol to the esterification reactor, the terephthalic acid in the slurry tends to form lumps due to the high ratio of terephthalic acid. This causes trouble in that the slurry supply system is blocked, making it impossible to supply the slurry.

Recently, various proposals have been made to improve this type of trouble.

For example, there is a method of cooling the inlet of the esterification reactor (Japanese Patent Publication No. 42-16077), a method of inserting a heat insulating material into the inlet of the esterification reactor (Publication of Utility Model Publication No. 1179-1973), and a method of controlling the slurry temperature. Method of
No. m, JP 49-33946, and JP 50-1
2043) and a method of lowering the slurry molar ratio (Japanese Unexamined Patent Publication No. 52-7143). However, with these known methods, although it is possible to reduce the clogging trouble when supplying slurry to some extent, it is not possible to completely eliminate the clogging problem, and therefore a large amount of time is required to treat the clogging trouble. The reality is that it takes effort and interferes with driving.

Moreover, each of the above methods is associated with specific drawbacks.

For example, the method of maintaining the slurry temperature at a relatively low temperature has a problem in that extra energy corresponding to sensible heat must be added to the esterification reactor to raise the low temperature slurry to the reaction temperature. In addition, if the manufacturing method and manufacturing conditions of terephthalic acid are different, the properties such as particle shape and particle size distribution will change. Depending on the nature of the acid, the slurry exhibits almost no fluidity, so there is a problem in that the slurry cannot be supplied to the esterification reactor without the use of special equipment such as an extruder. Moreover, in the latter method,
There is a problem in that the life of the device is shortened because a load is always applied to the device. Therefore, the inventors of the present invention have conducted intensive studies to establish a method for supplying the slurry to the esterification reactor, which solves the above-mentioned problems, and have arrived at the present invention. Therefore, the purpose of the present invention is to The object of the present invention is to improve the fluidity of a slurry of terephthalic acid and ethylene glycol, and eliminate any clogging of the slurry in a supply pipe for supplying the slurry to a terephthalic acid esterification reactor.

This objective is achieved by applying a method of supplying a slurry of terephthalic acid and ethylene glycol to the esterification reactor through the supply pipe while applying vibration to the slurry. . Note that the above-mentioned vibration may be performed continuously or intermittently. Hereinafter, the method of the present invention will be specifically explained in detail with reference to the drawings.

First, the slurry in the present invention refers to a homogeneous mixture of terephthalic acid and ethylene glycol, and impurities that are mixed into the mixture during the terephthalic acid manufacturing process, such as p-formylbenzoic acid, p-toluic acid, Of course, impurities such as diethylene glycol, water, etc. that come into the production or recovery/purification process of benzoic acid, ethylene glycol, etc.
In the present invention, slurry also includes catalysts, additives, copolymerization components, or small amounts of additives for improving the fluidity of the slurry, such as water and alcohols. .

When components other than terephthalic acid and ethylene glycol are mixed into the slurry and used, the components may be added into the slurry forming apparatus or may be added to the prepared slurry in the supply line. The molar ratio of terephthalic acid and ethylene glycol in the slurry is expressed as the number of moles of ethylene glycol per mole of terephthalic acid. It depends. For terephthalic acid with various properties obtained under different production conditions, the fluidity of the slurry was examined by changing the molar ratio and temperature. C. to 190.degree. C., if the molar ratio is 4.0 or more, the fluidity is very good, and there is no need to improve the slurry supply piping as in the present invention.
Therefore, the preferable range of the molar ratio of the slurry in the present invention is 2.5 or less when the slurry temperature is 100°C or less, and 10
It is 4.0 or less at 0 to 190°C. Such a slurry is prepared and supplied to the esterification reactor according to the manufacturing flow shown in FIG.

That is, terephthalic acid and ethylene glycol are supplied from supply pipes 2 and 3, respectively, to a slurry forming apparatus 1 for producing a slurry of terephthalic acid and ethylene glycol, and the obtained slurry is stored in the storage tank 4, and then The slurry is taken out from the take-out pipe 8 at the bottom and passed through the supply pump 5 and supply pipe 7 to the esterification reactor 6.
The slurry is supplied to the Slurry blockage 5, which the present invention aims to solve, refers to the primary side of the pump 5, that is, the take-out pipe 8, the bent part of the supply pipe 7, the vertically piped part, the valve, and the esterification reaction vessel. This occurs at the entrance to 6.

Therefore, in the method of the present invention, vibrations are applied to the slurry passing through the region of the tube that is likely to become clogged.

In the present invention, giving vibration to the slurry means a movement that disturbs the steady flow of the slurry. As a specific means, mechanical vibration is applied to the slurry supply pipe 7 from the outside,
Indirect or direct vibration, such as a method of indirectly transmitting this vibration to the slurry, and a method of directly applying vibration to the slurry by bringing an oscillator of an ultrasonic transmitter into contact with the slurry pipe and irradiating the slurry pipe with ultrasonic waves. There is a law. As a method of vibrating the slurry supply pipe 7, a stick-on type electromagnetic vibrator is typically used. Furthermore, as a direct method, in addition to the above-mentioned ultrasonic waves, there is a method in which the slurry supply pump 5 is operated intermittently, or a pressurized gas or a pressurized liquid is sent into the slurry supply pipe 7 to intermittently operate the slurry. There are methods to give unsteady motion. In this case, a gas inert to the esterification reaction system, such as nitrogen gas, is used as the pressurized gas, and water or ethylene glycol, etc., which does not inhibit the esterification reaction or have an adverse effect on the reaction product, is used as the pressurized liquid. To be elected. As a pump for feeding gas or liquid, a plunger pump with pulsation is suitable, but if it is a pump without pulsation, it is preferable to operate it intermittently. The first diagram shows a typical process diagram for carrying out the method of the present invention.
As shown in the figure, in addition to the second type slurry forming apparatus 1 shown in FIG. 1, a blow jet mixer type as shown in FIG. 2 can be used.

As for the slurry supply line, in addition to the single supply line shown in FIG. 1, an external circulation line 11 is installed in the slurry storage tank 4 as shown in FIG. While circulating, a plurality of branch pipes 12, 13, and 12 provided in the middle of the circulation line 11
... A method may be adopted in which the slurry is distributed and supplied from the supply pump 5 to the esterification reactor 6 through the supply pipe 7. In these cases, the inlet side of the supply pump 5,
One or more vibrating devices 9 may be provided on the outlet side or the inlet side of the slurry reactor 6. No.
FIG. 63 shows a process diagram in which a press-in pipe 19 having a press-in pump 18 is connected in the middle of the supply pipe 7, so that the press-in fluid can be intermittently press-injected into the slurry.

The slurry supply pump and circulation pump are preferably of non-compressible type, and such pumps include, for example:
I can give you a snake pump. The feeding of the slurry according to the invention can be carried out both in a continuous esterification reaction and in a batch esterification reaction.

Furthermore, the method of the present invention can be applied whether the esterification reaction is carried out under pressure, normal pressure or reduced pressure. If a slurry supply line is blocked in a continuous esterification reaction and attempted to be restored using conventional methods, it would take a long time for the operation to return to normal, and a large amount of polymer of different quality would be produced. According to the method of the present invention, it is possible to completely eliminate blockage of the supply line, and even if blockage occurs, normal operation can be restored in an extremely short period of time.Therefore, there is no loss of product due to trouble, and therefore terephthalic acid and There is an extremely effective method for supplying an ethylene glycol slurry to an esterification reactor. In addition, in a batch esterification reaction in which slurry is continuously supplied during the first half of the reaction, and then the slurry supply is stopped and the reaction is carried out until a predetermined reaction rate is reached, conventionally, while the slurry supply is stopped, the slurry is continuously supplied. This may cause the load on the feed pump to increase when starting slurry feed next time.
Although there have been cases where supply was not possible, according to the method of the present invention, this kind of trouble can be resolved, and furthermore, the method of the present invention is effective. Even when there is no blockage in the slurry supply pipe, the method of the present invention can systematically improve the fluidity of the slurry flowing in the supply pipe, reducing the load on the slurry supply pump, and ultimately This can significantly extend the life of the pump. Adoption of the method of the present invention does not significantly increase equipment costs, and therefore requires low investment in equipment. Hereinafter, the present invention will be explained in detail with reference to Examples. Example 1 Terephthalic acid A shown in the table below and ethylene glycol were added to the supply pipe 2 of the continuous slurry forming apparatus (kneader) 1 shown in FIG. 1 so that the molar ratio defined above was 1.1.
and 3 were respectively supplied to the apparatus to form a uniform slurry, which was transferred to the slurry storage tank 4.

Next, using a slurry supply pump (snake pump) 5 connected to the bottom of the storage tank 4, the slurry was continuously supplied at a rate of 50e1hr to the normal pressure esterification reactor 6 maintained at 260°C to carry out a continuous esterification reaction. did. A pressure gauge was installed on the secondary side of the snake pump 5 to detect the pressure inside the piping (supply pipe). The supply pipe 7 from the pump 5 to the esterification reactor 6 has a diameter of 2 inches (5.08 cm) and a length of 57F1. It was hot. 25Cj! from the connection between the esterification reactor 6 and the slurry supply pipe 7 to the outside of the supply pipe for 1 TrL on the supply pump 5 side! Stick-on type electromagnetic vibrators 9 were attached at intervals. The temperature of the slurry at the inlet of the esterification reactor 6 rises due to heat transfer from the reactor 6 and reaches 80°C.
It was hot. Although the vibrator 9 was operated continuously for 14 days, no blockage trouble occurred in the slurry supply pipe 7, and the pressure on the secondary side of the supply pump 5 was 0.7.
It was stable at ~1.0k91cF1fG.

Example 2 An experiment was conducted under the same conditions as in Example 1 and the steps shown in FIG.

However, the vibrator 9 was operated intermittently. When the pump 5 was operated with the vibrator 9 activated, the pressure on the secondary side of the pump 5 was 0.8k91cItG, but when the operation of the vibrator 9 was stopped, the pressure rose to 6k91cF1fG in 3 hours. When vibrator 9 was activated once, the pressure recovered to 0.8k9 AlG. When I stopped the vibrator 9 again, it was still 6.3 hours after 3 hours.
The pressure on the secondary side of the pump 5 rose to 1 kgIdG. Vibrator. As a result of intermittent operation in which the operation of step 9 was repeated once every 3 hours, slurry could be continuously supplied for 14 days, and there were no blockage problems in the supply pipe 7. The secondary pressure of the supply pump 5 is 0.
8-1.1k91cF1fG~5.8-6.7k91c
! Obtained from IG. Comparative Example 1 As a comparative experiment, an experiment was conducted in the same manner as in Example 1 in the steps shown in FIG. 1 without operating the vibrator 9.

As a result, the pressure on the secondary side of the snake pump 5 exceeded the allowable pressure of 12k91cT1G in 4 hours, and the pump became inoperable. Example 3 In the same manner as in Example 1, a continuous experiment was conducted for 14 days using terephthalic acid B1, terephthalic acid C, and terephthalic acid D having the particle size distribution shown in the table above as terephthalic acid in the process shown in FIG. Summer.

No matter which terephthalic acid was used, there was no clogging trouble in the supply pipe, and stable supply was possible. The pressure on the secondary side of the pump is 0.3 corresponding to each of the terephthalic acids.
~0.4k91c! 1G11.5~2.0k91c1t
It was G10.9-2.3k91c11G. Example 4
A slurry of terephthalic acid A and ethylene glycol with a molar ratio of 1.3 having the particle size distribution shown in the table above is processed using a continuous slurry device (blow jet mixer) shown in Fig. 2.
I made it with 1.

The obtained slurry was transferred to a slurry storage tank 4, and using a circulation pump (snake pump) 10 connected to the bottom of the storage tank, it was pumped to a slurry with a diameter of 4 inches (10.16c71) and a length of 507T.
1. The slurry was circulated through the circulation line 11 at a flow rate of 8 dIhr. In the circulation line 11, 5 Wi. 5 branch pipes 12, 13 for each
, 14, 15, and 16 are branched, and they are connected to the supply pipe 7 of the esterification reactor 6 via the circulation pump 5 (in Fig. 2, the supply pipe 7 is connected to the branch pipe 15 via the supply pump 5). A pressure gauge was installed on the secondary side of the supply pump 5. Branch pipe 1
5 is connected to the supply pump 5 at a point 27TL from the branch point 17 of the circulation line 11, and the supply pipe 7 is connected to the supply pump 5 at a point 27TL from the branch point 17 of the circulation line 11.
It was connected to the esterification reactor 6 at 47TL from the reactor. The supply pipe 7 extending 1 m from the inlet of the reaction vessel 5 was a double pipe cooling jacket 20, and 20° C. cooling water was passed therethrough at a rate of 1 f/min. Cooling jacket 20 to 10cm
and 1 each at a location 10 cm from the primary side of the supply pump.
An ultrasonic generator 9 that generates ultrasonic waves with a frequency of 6 to 150 kilocycles/second was attached. Esterification reactor 6
is a batch type reaction vessel, in which the same amount of reaction product as that obtained from the slurry supplied per batch is preheated to 250°C in the reaction vessel, and the above slurry is added thereto for 600 fIhr. It was continuously fed for 3 hours at a rate of . Thereafter, the supply of the slurry was stopped, and the reaction was continued until the esterification reaction was substantially completed. The reaction temperature during the slurry supply was 240°C to 242'C, and was controlled at 250°C after the slurry supply was completed. The reaction time for esterification is 5 hours, so the time the slurry remains stationary in the branch pipe and supply pipe is 2 to 2 hours3.
Gin de Atsuta. Two ultrasonic generators 9 are constantly operated, 5
When continuous operation of 0 batches is performed, the secondary pressure of the supply pump is always 0.1 to 0.3k91cG, and no slurry clogging occurs in the slurry supply pipe to the esterification reactor and the branch pipe. Ta. Comparative Example 2 An experiment similar to Example 4 was attempted without activating the ultrasonic generator.

From around the time when the 12th batch experiment was completed, the pressure on the secondary side of the supply pump 5 gradually increased, and at the 18th mark, the pressure exceeded the allowable pressure of 8 kgIcItG, and operation became impossible.

When the supply pipe 7 and the branch pipe 15 were disassembled and inspected, the presence of clogging in the form of lumps of terephthalic acid near the cooling jacket 20 at the primary side of the supply pump 5 and the inlet of the esterification reactor 6 was confirmed. Example 5 Terephthalic acid A having the particle size distribution shown in the above table and ethylene glycol were mixed at a molar ratio of 1.85 to prepare a slurry, and the method of the present invention was tried in the step shown in Part 3.

That is, the slurry is passed through the take-out pipe 8 and the supply pump 5.
The esterification reaction was carried out by continuously supplying the mixture at a flow rate of 0e1hr to the atmospheric pressure esterification reactor 6 maintained at 270°C. The supply pipe 7 for supplying slurry from the supply pump 5 to the esterification reactor 6 has a diameter of 2 inches (50.8
cm) It was hot. Incidentally, on the secondary side of the pump 5, there is a pressure gauge for detecting the pressure of the supply pipe, a pressurized ethylene glycol press-fit pipe 19, and a press-fit pump (plunger pump).
18 were installed. 1e from the start of operation! ! ! During this period, the pressure on the secondary side of the supply pump 5 went from 0.7 to 10k91cILG.

Therefore, when pressurized ethylene glycol was forced into the supply pipe 7 from the press-fit pipe 19 and the slurry was vibrated, 2
After a minute, the pressure on the secondary side of the supply pump 5 is 0.5k91c.
I went down to dG. Thereafter, the feeding of pressurized ethylene glycol was stopped, normal operation was continued, and when the pressure on the secondary side of the supply pump 5 reached 10k91cItG, pressurized ethylene glycol was repeatedly press-fitted from the press-fitting pipe 19. .
This operation was repeated every 13 to 1 minute, and the pressurized ethylene glycol was repeated every 2 to 4 minutes, and the operation was continued for 14 days, but no problems with clogging the supply pipe 7 occurred. Ta.

[Brief explanation of the drawing]

FIG. 1 is a typical process diagram for carrying out the method of the present invention.
FIGS. 2 and 3 are process diagrams carried out in another manner. 1... Slurrying device, 4... Storage tank,
5... Supply pump, 6... Esterification reactor, 7... Supply l pipe, 9... Vibration device.

Claims (1)

[Claims] 1. A slurry of terephthalic acid and ethylene glycol, characterized in that when the slurry of terephthalic acid and ethylene glycol is supplied to the esterification reactor through the supply pipe, the slurry is supplied with vibrations. How to feed the reactor.