JPS6089448A - Continuous production of terephthalic acid glycol ester - Google Patents

Abstract

PURPOSE:To produce high-quality BHET continuously, in high efficiency, by reacting terephthalic acid with ethylene glycol using mutually connected plural reaction chambers, taking out a part of the product from the first reaction chamber, and recovering the product together with the BHET delivered from the last reaction chamber. CONSTITUTION:In the continuous production of terephthalic acid glycol ester (BHET) by the reaction of terephthalic acid with ethylene glycol, the reaction is carried out in mutually connected plural chambers, preferably 2-3 chambers, especially two chambers. A part of the esterificaton reaction product containing unreacted terephthalic acid particles as suspended matter is taken out of the first reaction chamber, and filtered to obtain a product free from the unreacted terephthalic acid particles. The product is combined with the BHET delivered from the last reaction chamber to obtain BHET having various characteristics and having low by-produced diethylene glycol content, in high efficiency. The residual part of the reaction mixture of the first reaction chamber is transferred to the second reaction chamber.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention produces terephthalic acid glycol ester, that is, bis(β-hydroxyethyl) terephthalate and/or its low polymer ( BIIIET) with a low diethylene glycol (DUG) concentration.

The present invention provides a method for simultaneously and efficiently producing IETs with different properties, including BIIETs that can form polyesters with good heat resistance.

Polyester is used industrially today.

In particular, polyethylene terephthalate is highly crystalline.

It has a high softening point and excellent properties in terms of strength, chemical resistance, heat resistance, weather resistance, electrical insulation, etc., so it is widely used industrially as fibers, films, and other molded products. has been done.

In general, when polyester is used in various industrial fields, it usually requires heat resistance during forming processes such as melt extrusion, drawing, stretching, and heat treatment, or in the case of films, heat resistance during coating of magnetic layers and metal vapor deposition. Heat resistance is required in the secondary processing process when molded products are made, and also heat resistance when the final products are made.

For this purpose, D in the polyester resulting from side reactions is required.
Reducing the HiJ degree is considered to be one important issue. Polyester is usually produced by an esterification process followed by a polycondensation process, but traditionally,
In the esterification process, which has a large influence in order to reduce the DUG concentration, efforts have been made to develop and improve catalysts and additives, and to develop processes that can reduce the DUG concentration, but at the same time, they also have some drawbacks. was.

For example, including Japanese Patent Publication No. 34-2594.

Although the addition of alkali metal compounds as catalysts and additives, which have been proposed many times, contributes to reducing the DUG concentration, it also impairs color tone, viscosity, strength, and other physical properties, and may cause pentacondensation. This has the disadvantage of causing speed delays.

On the other hand, as a process for reducing the DEC concentration, a conventional process has been to carry out a transesterification reaction between dimethyl terephthalate and EG. There was a transesterification method for producing TPA, but it was not suitable for continuous operation and dimethyl terephthalate was more expensive than TPA.

Moreover, compared to the transesterification method, TPA and EG are directly esterified. This is because the so-called direct esterification method has advantages such as a simpler process.

Gradually, the process shifted to direct esterification, which continues to be the case today. Therefore, even if the cost amplifier is a little higher now, it is especially low D.
Generally, the transesterification method is used only for varieties that require high IEG concentrations.

Now, even when the above-mentioned direct esterification method is adopted, high quality Bll[! A method for manufacturing T has also been proposed.

For example, as disclosed in Japanese Patent Publication No. 46-22463, TPA is suspended in BIIET and IEG
As disclosed in JP-A No. 50-24236 and a method of reacting gaseous EG at a temperature higher than the boiling point of By separating the TPAP molecules, the reaction rate is constant and the BII [! Methods for obtaining T have been proposed.

However, even when these methods are adopted, in the former case, variations in the per-reaction rate and DEC concentration occur, which is a problem, and in the latter case, if the salinity per reaction is lowered, one mouth [! Although the G concentration is reduced, there are problems in that productivity is poor and the system becomes extremely unstable when the reaction rate fluctuates due to disturbance.

In this way, high quality B111 with low DEC concentration! What is the method for continuously and efficiently producing T using a direct esterification method?

It could not be said that it had been fully industrialized yet.

As a result of extensive research in order to solve this problem, the present inventors conducted a reaction using a plurality of consecutive reaction vessels,
In addition to taking out the reactant from the final reactor as a product, a portion of the reactant from the first reactor is filtered to remove unreacted TPAP particles and taken out as a product. .

BII with different properties including BIIET with low oucz degree
The present invention was completed by discovering that ET can be obtained efficiently.

That is, one aspect of the present invention is TPA and t! BI by reacting with G
When continuously producing IET, nine reactions are performed using two or more consecutive reaction vessels, and unreacted T from the first reaction vessel is
A part of the esterification reaction product in which PAP molecules are suspended is filtered to remove unreacted TPAP molecules and taken out as a product, and the remainder is transferred to a second reaction tank. It is something to do.

The method of esterification in the present invention is 2 usually 111
In the reaction tank where 1ET is present, T'P^ and I! A method is used in which a slurry consisting of G is continuously supplied and esterified. This BIIET may partially contain components other than TIIA and EG residues, and BIIE
T may be obtained by any known method.

It is preferable to use the material obtained by the above method as it is. The raw material is usually supplied as a slurry consisting of TPA and EG, but the slurry [! The molar ratio of G/TPA is usually 1.2 to 2.0. The angle is preferably 1.4 to 1.8 degrees, most preferably 1.5 to 1.7 degrees. Of course, this slurry also contains some other acid components such as isophthalic acid, 5-sodium sulfoisophthalic acid, adipic acid,
sebacic acid, naphthalene dicarboxylic acid, diphenylsulfone dicarboxylic acid, etc. or other glycol components such as tetramethylene glycol, neopentyl glycol,
114-cyclohexane dimetatool and the like may be contained to an extent not exceeding 30 mol%.

In addition, the esterification reaction may be carried out at normal pressure or at elevated pressure, but in order to suppress the DEC concentration,
．． 5kg/cJ or less, preferably 0.15kg/c+
1 or less, most preferably 0.05 kg/- or less.

On the other hand, the temperature of the esterification reaction is usually 220 to 270°C.
1 Preferably 240-270°C, optimally 250-26
It is 0°C. If the temperature is lower than 220°C, the esterification reaction will not substantially proceed, while if it exceeds 270°C, the DIEG concentration will increase, which is not preferred.

When esterification is carried out in the 1ml method, when the esterification reaction rate reaches about 90%, suspension of unreacted TP^ particles is no longer observed and the 1 reactant becomes transparent. However, if it is fed as is to the polycondensation step, which is the second step in polyester production, the reaction rate will decrease, causing a delay in the first polycondensation time, and the amount of BIIET from low-density synthetic leather will increase, so it is difficult to reduce the raw material consumption rate. This is because it is undesirable because it may cause deterioration or blockage of the distillate vapor extraction system that goes into the pentacondensation process.

Tsutomu needs to react until B11IuT is produced at a relatively high reaction rate of 90 to 98%, preferably 93 to 98%, optimally 94 to 96%, and as a result, This will lead to a decrease in productivity and an increase in the D[G concentration.

It has been known to increase the reaction efficiency and suppress the increase in DUG concentration by carrying out the esterification reaction using several consecutive tanks, but it is not economical to increase the number of tanks unnecessarily. However, there are naturally limits to suppressing the DUG concentration.

However, according to the method of the present invention, a plurality of tanks 3, preferably 2 to 3 tanks, as many as are normally used.

Optimally, when continuously producing BIIET using two continuous tanks, the overall esterification reaction rate in the first reaction tank is set to a state where unreacted TPA particles are suspended, and the reaction from the first reaction tank is A part of the reactant is filtered to remove unreacted TP^ particles and taken out as a product (BIIET), and together with BIIET from the final reaction tank, it is sent to the next polycondensation reaction step tailored to the final polymer application. By providing this, the object of the present invention is achieved.

If the temperature and pressure of the reaction tank are kept constant, 811 after filtration
1! As disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 50-24236, etc., T has constant characteristic values such as esterification reaction rate and number average degree of polymerization. ~It will look like Figure 3. Figure 1 shows the relationship between the reaction temperature and the reaction rate of BIIET after filtration, Figure 2 shows the relationship between the overall esterification reaction rate and the DEC concentration in BIIET after filtration, and Figure 3 shows the relationship between the overall esterification reaction rate and the DEC concentration in BIIET after filtration. BIIIE after filtration
Relationship between T and reaction rate (reaction temperature 250°C and 260°C
) are shown respectively.

When reacting using only one tank, i+ with stable characteristics
In order to obtain tt+T, the temperature and pressure must be kept constant, and as shown in Figure 1, in order to obtain B111uT with an esterification reaction rate of 94-96%, which is most suitable for the polycondensation process, the temperature and pressure must be kept constant at 250 °C. It is necessary to maintain the temperature at a constant temperature below, which has the disadvantage that the reaction rate becomes low and productivity does not increase.

Furthermore, if the overall esterification reaction rate including unreacted TP^ particles is about 85%, the substantial reaction capacity will decrease and the reaction efficiency will also deteriorate.

By the way, in the current era where small quantities of polyester are desired in many varieties, it goes without saying that BIIET, which is an intermediate product, is also required in many varieties.

According to the method of the present invention, by changing the temperature, pressure, and feed rate of raw materials in the first reaction tank to change the overall esterification reaction rate, different quality BIII! This makes it possible to obtain T at the same time.

In the present invention, any known filtration device can be used to filter one reactant, but it is effective to use a filter with a mesh size of 10 to 100 μm, preferably 20 to 60 μm, and most preferably 30 to 50 μm. It is true. Even if the mesh size is finer than this range, not only will the filtration effect become saturated, but it will also undesirably increase the pressure loss and shorten the filter life.
If the mesh size is coarser than this range, unreacted TPA particles will not be sufficiently filtered and will come out through the meshes of the filter.

Both are undesirable.

It is also possible to install this filter at the bottom of the reaction tank and take out only the BIIET that does not contain unreacted TPA particles, but it is also possible to install an independent filtration device outside and have one inlet and two outlets. The use of
preferable. That is, a polycondensation process in which unreacted TPA particles passed through an inlet and a filtration layer in which an amount of reactant is introduced in excess of the actual production amount, preferably several times the production amount, in which unreacted TPA particles are suspended, are removed. BIIET supplied to the reaction process
A filtration device having an outlet for discharging (corresponding to the actual production amount) and an outlet for recycling or transferring the increased reactant of remaining unreacted TPA particles to the next reaction vessel is preferred; By using the device, the filtration process can be operated smoothly and with a long service life.

FIG. 4 is a flow sheet showing one embodiment of the present invention, where 1 is a first reaction tank, 2 is a second (final) reaction tank, and 3 is a TP
Raw material supply line that supplies slurry of A and [G, 4
5 is the EG supply line, 5 is the liquid feeding line from the first reaction tank to the second reaction tank, 6 is the reactant dispensing pump, and 7 is the filtration device.
The IUT is sent to the polycondensation step via a liquid feed line 8, and the remaining reactant, which has an increased amount of unreacted TP^ particles due to filtration, is recycled to the first reaction tank via a recycle line 9. Further, BIIET from the second reaction tank is sent to the polycondensation process via the liquid feed line 10.

FIG. 5 is a flow sheet showing another embodiment of the present invention, in which the reactant from the first reaction tank is supplied to the total volume filtration device,
The remaining reactant, in which unreacted TPA particles have increased due to filtration, is transferred to the second reaction tank via a liquid transfer line 11.

As shown in the embodiment examples, it is preferable to attach the filtration device only to the first reaction tank and not to the other reaction layers because control is easier.

Hereinafter, the present invention will be specifically explained with reference to Examples.

In the examples, "parts" indicate parts by weight, and the characteristic values were measured by the following method.

+11 LIIEG concentration (mol%) Produced by alcoholysis for 2 hours under refluxing methanol [
G and 1) IuG were analyzed and quantified by gas chromatography.

(2) Reaction rate f (%) Calculated using the following formula from the acid value (AV) determined by the method described below and saponification 1m (SN).

N O acid value (8 V) (equivalent/ton) Accurately weigh about 3 g of sample and add dimethylformamide 40
ml under reflux, and after cooling, the solution was determined by potentiometric titration with a 1/10 normal methanolic potassium hydroxide solution.

0 Saponification number (SN) (equivalent/ton) Approximately 0.5 g of the sample was accurately weighed and alkaline hydrolyzed with excess 1/2 N ethanolic potassium hydroxide solution at 20°C for 1 hour to remove excess potassium hydroxide. was determined by back titration with 1/2 normal hydrochloric acid.

Example 1 Using the apparatus shown in FIG. 4, B111! 102 parts/Ilr of slurry with an EG/TPA molar ratio of approximately 1.6 was placed in the first reaction tank 1 containing T, and 5 parts/Ilr of UG was placed in the second reaction tank 2.
The first reaction tank has a temperature of 255°C, a pressure of 0.05kg/c+a G, and an average residence time of 6 hours, and the second reaction tank has a temperature of 255°C and a pressure of 0.05kg/c+aG.
, when the reaction was carried out at an average residence time of 3.5 hours, the first
The overall esterification reaction rate of the reaction tank is 80%, the overall esterification reaction rate of the second reaction tank is 94%, and the esterification reaction rate of DIIIET after filtering the reactant from the first reaction tank is 94%.
, 1st and 2nd reaction tank empty (D BIIET (7) D
[iG ij 1 degree was 0.110 mol% and 1.12 mol%.

The amount transferred from the first reaction tank to the second reaction tank is 52 parts/
It was set to 11r. Also, as a filter, the mesh size is 40.
Using a stainless steel plain-woven wire mesh, the amount supplied to the filtration device was 125 parts/llr, and BIIIET was added to the polycondensation step at a rate of 25 parts/llr from the first reaction tank and 52 parts/11r from the second reaction tank. sent.

Example 2 Using the apparatus shown in Fig. 5, the amount of slurry supplied to the first reaction tank was 110 parts/Ilr, and the amount of EG supplied to the second reaction tank was 6 parts/Ilr.
parts/llr, and the reaction was carried out under the same conditions as in Example 1.

The properties of the esterification reaction product and Bll[iT are almost the same as in Example 1, and B111! The production amount of T is 20 parts/Ilr from the first reaction tank and 63 parts/11r from the second reaction tank.
Met.

Comparative Example In Example 1, a filtration device was not attached to the first reaction tank, and the entire amount of the reactant from the first reaction tank was transferred to the second reaction tank as it was, so that the amount of slurry supplied to the first reaction tank was 1
10 parts/Ilr, EG supply amount to the second reaction tank 8 parts/l
lr, and the reaction was carried out under the same conditions as in Example 1.

The obtained BIIBT had an esterification reaction rate of 94%, DE
At a C concentration of 1.10%, the production amount was 83 parts/11r.

As described above, according to the method of the present invention, BIIIET with a low DIltGa degree and IIIET with a normal DEC concentration can be efficiently produced simultaneously.

[Brief explanation of the drawing]

Figure 1 shows the relationship between reaction temperature and reaction rate of old JET after filtration, Figure 2 shows the overall esterification reaction rate and BIIBT after filtration.
Figure 3 is a graph showing the relationship between the overall esterification reaction rate and the reaction rate of BII[iT after filtration, respectively. Figures 4 and 5 show embodiments of the present invention. It is a flow sheet. 1-first reaction tank, 2-second reaction tank. 3-raw material supply line, 7-filtration device. Patent applicant Nippon Ester Co., Ltd. Agent Yuji Tama 11 times 11 times ￥21] Ester-containing reaction ↑ (%) ￥3 times

Claims (1)

[Claims] +11 When terephthalic acid and ethylene glycol are reacted to continuously produce terephthalic acid glycol ester, nine reactions are performed using two or more consecutive reaction vessels, and unreacted terephthalic acid particles from the first reaction vessel are Terephthal, which is characterized in that part of the suspended esterification reaction product is filtered to remove unreacted terephthalic acid particles and taken out as a product, and the remainder is transferred to a second reaction tank. Continuous production method for acid glycol esters.