JPS63277230A - Method for ester interchange reaction - Google Patents

Abstract

PURPOSE:To carry out ester interchange with good productivity and stable operation, by adding a catalyst in a specific proportion in obtaining bis- hydroxyethyl terephthalate from dimethyl terephthalate and ethylene glycol. CONSTITUTION:(A) Dimethyl terephthalate is reacted with (B) ethylene glycol by a batch method to provide (C) bis-beta-hydroxyethyl terephthalate (low polymer). In the process, (D) 5-50wt.% ester interchange reaction catalyst is added in the first stage to start reaction. The residual 50-95wt.% component (D) is then added when the reaction temperature attains <=150 deg.C to complete the reaction. Thereby the aimed ester interchange is carried out.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention provides bis-β-hydroxyethyl terephthalate and/or The present invention relates to an improved industrial batch transesterification method for obtaining the low polymer (hereinafter referred to as BHT).

(Prior art) Polyethylene terephthalate (hereinafter referred to as PET) is
Due to its excellent physical and chemical caustic properties, it is widely used in fibers, films, bottles, etc.

Known methods for producing PET include a transesterification method using DMT and NG as starting materials, and a direct polymerization method using terephthalic acid and BG as starting materials.

(Problems to be Solved by the Invention) A problem with the conventional batch process consisting of the transesterification reaction of DMT and EG is that the reactor is at a high temperature after the transesterification reaction is completed, and therefore the DMT and EG ( 7)
G dissolution is the transesterification reaction. At the point when the catalyst is introduced,
The reason is that it is 1. If the transesterification reaction catalyst is added in this state, a rapid reaction will occur, causing bumping and other instability, and the reaction will become unstable! This DMT sublimes and clogs the rectification column for removing methanol generated from the reaction solution, resulting in an extremely unfavorable phenomenon in terms of operation.

In order to prevent this, it is necessary to wait until the temperature of the reactor drops after the end of the pre-patch reaction, or until the temperature of the DMT and EG solution added to the reactor drops, resulting in extremely poor productivity. A problem arises.

In order to solve this problem, there is a method in which the total amount of EG is first supplied to the reactor before the reaction, and then DM'I' is supplied at a specific ratio to cause the reaction (Japanese Patent Publication No. 15785/1985), A method in which 90% or less of EG in the reaction ξ is initially present, and then the remaining EG is continuously supplied at any stage when the reaction rate of DMT is 80% or more. No. 8050) has been proposed. However, in these methods, the driving operation and W-processing are complicated, and the productivity is not as high as expected. Furthermore, the anv method produces a large amount of diethylene glycol (hereinafter referred to as "FDEG") as a by-product, which has the disadvantage of lowering the softening point of the polymer obtained from the product HT.

The present inventors have arrived at the present invention as a result of intensive studies aimed at improving the drawbacks of the conventional transesterification method of DMT and EG. That is, the first object of the present invention is to improve the biomolecular properties of the transesterification reaction (
The purpose of this invention is to provide a method for producing BHT that is stable, f', and operationally controllable. The second purpose is to obtain by-product DEG.
The purpose of this invention is to provide an improved manufacturing method for BHT that makes it possible to obtain high-quality PET.

(First Means to Solve the Problems) That is, the method of the present invention involves reacting DMT and EG in a batchwise manner to produce BHT and/or its low polymer. ~50 weight 1%
was initially added to start the reaction, and the temperature of the reaction solution was 150℃.
``C or less'' (this is characterized in that the remaining 50 to 95% by weight of the transesterification catalyst is added to complete the reaction.

Conventionally, DMT and KO are reacted batchwise (at this time, DMT and EGQ are added at the time of adding the transesterification catalyst).
Since the temperature of the solution is high, bumping occurs due to rapid reaction, which causes DMT to sublime and clog the rectification column. Therefore, in the method of the present invention, 5 to 50 transesterification catalysts are used for one reaction. ! Add the amount% first,
Allow the reaction to proceed slowly. As the reaction progresses, methanol is distilled out, and its latent heat of vaporization is used to lower the temperature of the reaction solution to 150° C. or lower. After that, 50-9 remaining
In this method, the transesterification reaction is stably completed by adding 5 iJt% of the transesterification reaction catalyst and gradually raising the temperature. According to this method, rapid reaction 1
This not only prevents bumping but also prevents clogging of the rectification column due to sublimation of DM'r.

It is important that the transesterification reaction catalyst initially added in the present invention Eζ is 6 to sogg%, preferably 10 to 40% by weight of the dish used for the reaction. 50! !
If Ik% is exceeded, transesterification reaction occurs rapidly, bumping occurs, and DM'I' solidifies and clogs in a rectification column or the like. On the other hand, if it is less than 5% by weight, the transesterification reaction will not proceed at a practical speed and the temperature of the reaction solution will not drop quickly due to the latent heat of vaporization of methanol, so it will take time to add the remaining catalyst. It requires a lot of effort and does not lead to the same increase in productivity.

The remaining catalyst should be added when the reaction solution has reached 150°C or lower. If the catalyst is added at a temperature higher than 150''C, a rapid transesterification reaction will occur, which is not desirable.

As the transesterification catalyst used in the method of the present invention, known compounds can be used, but calcium acetate, magnesium acetate, zinc acetate, manganese acetate, cobalt acetate, antimony trioxide, etc. alone or in combination are preferred. .

As additives, known particles such as titanium oxide, barium sulfate, calcium carbonate, kaolinite, talc, and silica may be added at any stage of the reaction. It is also possible to add known heat-resistant agents such as phosphorus compounds, ultraviolet absorbers, and antioxidants.

The method of the present invention can also be applied to transesterification methods that use 80 mol% or less of copolymer components in addition to DMT and EG. Copolymerization components include isophthalic acid dimethyl ester, 5-sulfosodium isophthalic acid dimethyl ester, phthalic acid dimethyl ester, 2,6-naphthalic acid dimethyl ester, 1,4-cyclohexane dimetatool, and methyl rosehydroxybenzoate. Examples include dicarboxylic acid esters such as esters, dicarboxylic acids such as adipic acid and sebacic acid, and alkylene glycols such as 1,4-butanediol, propylene glycol, and 1,6-hexanediol.

BHT obtained by the method of the present invention can be produced into fibers, films, and Fj! by a subsequent polycondensation reaction. PET having excellent quality as a resin molded product can be obtained.

(Effect of the invention) The effects of the present invention are as follows.

■ By setting the reaction starting temperature fζ, it is possible to shorten the cooling time of the reactor by one point when starting the next reaction, and there is no need to wait for the temperature of the DMT and NG solution to drop. Therefore, the productivity can be significantly increased by 1ζ.

(2) Even if the reaction start temperature is less than -C, stable operation can be carried out while avoiding clogging of the rectification column due to sublimation of DMT.

(2) According to the method of the present invention, pure quality BHT can be obtained with a constant molar ratio of DMT and EG.

(Example) The present invention will be further explained below with reference to Examples.

Example! The method of the present invention was carried out using a batch type transesterification reactor shown in FIG.

1T flakes 2,000 to D to heating tank (1) and EGl, 150Kf (EG/DMT molar ratio = 1.80)
was introduced into the transesterification reactor (2), which had completed the transesterification reaction of the previous batch and had become y.
a K Ha175-C(!: 'J-) r o Calcium acetate hydrate t as a catalyst in tank (2)
0.86 Kg (20% of the supernatant used in the reaction) I'! i to start the transesterification reaction. 5 minutes after the addition of the catalyst, methanol begins to be delivered from the rectification column (3), and the temperature of the reaction liquid decreases due to the latent heat of vaporization of methanol, reaching 146-C 20 minutes after the addition of the catalyst -1':. Then, the remaining 1.44Kp of transesterification catalyst was added, the temperature was raised from 145°C to 240°C at a rate of 25"C/H, and then 2
The transesterification reaction was completed by holding at 40°C for 15 minutes. During this period, there were no sudden reports of methanol, and the reported liquid was clear and DM'! No contamination of ' was observed, and no increase in pressure inside the reaction tank due to clogging of the rectification column was observed. Although 100 consecutive reactions were repeated using this method, there were no particular abnormalities (and stable operation was possible).

Example 2 When the solution of DMT and flG was transferred to the reaction tank (2) in the same manner as in Example 1, the temperature for dissolving 1 volume was 174°C.
It became. Calcium acetate-water salt TrO, 72Ky (40% of the amount used in the reaction) was added to this reaction tank (2) to start the transesterification reaction, but methanol was being rapidly produced (notifications began to be made in the rectification column). The top temperature rose to 78"C. However, 10 minutes after catalyst addition, the top temperature rose to 65"C.
The temperature of the reaction solution reached 145°C after 20 minutes. Then, the remaining transesterification catalyst 1.08 KF was added,
Thereafter, the reaction could be repeated smoothly as in Example 1.

Comparative Example 1 Same as Example 1 [The solution of DMT and EG was transferred to reaction tank (2) 1ζ, and the temperature of the solution was 175°C.
It became. When 1.80 Kf (100% of the capacity used for the reaction) of calcium acetate hydrate was added to this reaction tank (2), methanol was rapidly released and the temperature at the top of the rectification column rose to 9.
The temperature rises to 5°C, and the circular pressure in the reaction tank (2) rises to 0.
5 f/cm” G, and the reported liquid became cloudy and D.
Sublimation of the MT was so severe that it became impossible to continue operation.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a batch type transesterification reactor that can be suitably used in the method of the present invention.

Claims (1)

[Claims] When dimethyl terephthalate and ethylene glycol are reacted batchwise to produce bis-β-hydroxyethyl terephthalate and/or its low polymer, 5 to 50% by weight of the transesterification catalyst is added at the beginning to initiate the reaction. After starting and the reaction temperature becomes 150°C or less,
A transesterification method characterized in that the remaining 50 to 95% by weight of the transesterification catalyst is added to complete the reaction.