JPS6055501B2 - Production method of diaryl ester - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing diaryl esters.

More specifically, the present invention relates to an improved method for producing an aromatic dicarboxylic acid diaryl ester by esterifying an aromatic dicarboxylic acid and an aromatic monohydroxy compound in the presence of a specific medium. Conventionally, methods for producing aryl esters of aromatic dicarboxylic acids include (1) esterification reaction between aromatic carboxylic acids and aromatic monooxy compounds, and (2) esterification reactions between aromatic dicarboxylic acid alkyl esters and aromatic monooxy compounds. Methods such as transesterification and (3) transesterification of aromatic carboxylic acid and aliphatic carboxylic acid aryl ester are known.

Among these methods, the esterification reaction (1) is most preferred since the by-product is water. However, the esterification reaction product between an aromatic carboxylic acid and an aromatic monohydroxy compound varies depending on the catalyst used, but it is usually markedly colored, and it is difficult to separate the unreacted aromatic monohydroxy compound. have a defect. For example, when terephthalic acid is used as the aromatic carboxylic acid and phenol is used as the aromatic monohydroxy compound, the aryl ester obtained is solid at room temperature and contains unreacted phenol, making it difficult to handle. Also, the coloring is significant. For this reason, a method has been proposed in which the reaction product is transferred into a solvent such as xylene immediately after the reaction and purified by recrystallization or the like. Aromatic dicarboxylic acid aryl esters are known to be useful as polymerization accelerators for polyester, which is a material for fibers, films, etc., but whiteness is required for use as polymerization accelerators for other purposes. Therefore, it is desired to develop a method for easily producing diaryl esters with little coloring.

The present inventor conducted extensive research to find a method for easily producing a diaryl ester with excellent color tone, and found that by reacting an aromatic dicarboxylic acid and an aromatic monohydroxy compound in the presence of a specific medium, The present invention was achieved based on the discovery that a diaryl ester having a high reaction rate, easy reaction operation, and excellent color tone can be obtained.

That is, the present invention provides a method for producing an aromatic dicarboxylic acid diaryl ester by reacting an aromatic dicarboxylic acid with an aromatic monohydroxy compound in an amount of 2.1 to 10 times the mole of the aromatic dicarboxylic acid. 105-1
It is characterized by distilling off by-product water at 230 to 35 CfC in the presence of an aromatic hydrocarbon having a boiling point of 75°C (under normal pressure), and then separating the reaction product from the aromatic hydrocarbon. This is a method for producing diaryl ester.

Aromatic dicarboxylic acids used in the present invention include, for example, terephthalic acid, isophthalic acid, phthalic acid, naphthalene dicarboxylic acids (1●4, 2.6-, 2.7 monoisomers, etc.), diphenyl dicarboxylic acids, diphenyl ether dicarboxylic acids, etc. Examples include acids, diphenylsulfone dicarboxylic acids, diphenoxyethane dicarboxylic acids, and the like.

Among these, terephthalic acid and isophthalic acid are particularly preferably used. On the other hand, an aromatic monohydroxy compound is a compound in which one hydroxyl group is directly bonded to an aromatic ring, and includes, for example, phenol, cresol, naphthol, and the like.

Among these, phenol is particularly preferred. The ratio of the aromatic monohydroxy compound used to the aromatic dicarboxylic acid is 2.1 to 10 times by mole.

When this ratio is less than 2.1 moles, the reaction rate is slow, and when it exceeds 10 moles, the effect is saturated.
The effect of increasing the amount used was fully expressed. However, this is not preferable because it causes a defect that increases the capacity of the device.
The preferred amount of the aromatic monohydroxy compound used is 2.
The amount is 1 to 5 times by mole, more preferably 2.5 to 4.5 times by mole. Aromatic hydrocarbons used as a medium in the present invention are aromatic hydrocarbons having a boiling point of 105 to 175°C under normal pressure, such as toluene, xylene, ethylbenzene, cumene, cymene, trimethylbenzene, ethyltoluene, etc. can give.

Among these, ethylbenzene is particularly preferred. A medium having a boiling point of less than 105° C. under normal pressure is not preferred because the reaction pressure becomes high and the reaction rate, which is one of the objects of the present invention, is hardly increased. On the other hand, a medium with a temperature exceeding 175° C. is undesirable because the reaction rate becomes slow and the medium becomes colored. In the present invention, the aromatic dicarboxylic acid and the aromatic monohydroxy compound are reacted in the aromatic hydrocarbon medium to obtain the di-11J-lester of the aromatic dicarboxylic acid. is preferably present in the reaction system in an amount of 0.1 to 1 times the weight of the aromatic dicarboxylic acid, more preferably 0.3 to 5 times by weight, particularly 0.5 to 3 times by weight.

As a result, if the amount is small, the effect of using the medium of the present invention will be small, and if the amount is larger than this, the reactor will become larger and the reaction rate will decrease, which is not preferable. 2
It is desirable that it be before it reaches 0%.

In the reaction between an aromatic dicarboxylic acid and an aromatic monohydroxy compound, it is preferable to use a catalyst. As such a catalyst, any known catalyst for the above reaction can be used, such as titanium compounds,
Tin compounds, antimony compounds, etc. are preferably used. More specifically, titanate alkyl esters such as titanium tetrabutoxide and titanium tetrapropoxide, titanium salts of carboxylic acids such as titanium oxalate and titanium trimellitate, tin carboxylates such as tin acetate, Examples include organic tin compounds such as dibutyltin oxide, and antimony compounds such as antimony trioxide. The amount of catalyst used is preferably 0.001 to 5 mol % based on the aromatic dicarboxylic acid. The esterification reaction is usually carried out in a pressurized reactor equipped with a rectification column, and the water produced by the reaction is distilled out from the upper part of the rectification column.

In this case, it is preferable to distill both water and aromatic hydrocarbons as a medium, to separate the distillate into liquids, and to reflux the aromatic hydrocarbons back to the top of the column or another suitable location. . When such a method is used, there is an advantage that even if the aromatic monohydroxy compound is distilled off from the top of the column, it is dissolved in the aromatic hydrocarbon and returned to the system. However, it goes without saying that the present invention can be implemented not only by this method, but also by using devices other than those described above. The reaction is 230~
350°C, preferably 250-320°C for 30 minutes to 24
Implemented in hours.

At temperatures below 230°C, the reaction is extremely slow and cannot be used practically.

Further, temperatures exceeding 350°C are not preferred because coloration becomes significant and the reaction pressure becomes high. After completion of the reaction, the reaction product is preferably cooled to a temperature below the normal pressure boiling point of the aromatic hydrocarbon and then taken out.

In particular, precipitating the aromatic dicarboxylic acid diaryl ester by cooling to 100° C. or lower, or even 80° C. or lower, and extracting the diaryl ester in a solid state by solid-liquid separation is a process that simplifies extraction and purification. It is preferable that they can be done at the same time. At this time, the amount of aromatic hydrocarbon in the medium is preferably such that the precipitation and solid-liquid separation processes can be carried out advantageously. As mentioned above, one of the features of the present invention is that the reaction product can be taken out after cooling and purified by solid-liquid separation. Solid-liquid separation can be performed by conventional separation methods such as filtration and centrifugation. The present invention provides various advantages in the production of diaryl esters.

For example, there is no need to change the reaction pressure during the reaction to promote the distillation of water as a by-product, the reaction operation is easy, the reaction rate is fast, there is little coloring of the diaryl ester, and there is no need for cooling. (If a reaction medium is not used, the entire reaction product will solidify and it will be difficult to cool and remove it from the reactor), and the cooled product can be separated into solid and liquid. This provides advantages such as the ability to obtain purified diaryl esters. Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, parts in the examples mean parts by weight. Further, the color tone was determined using a hander type colorimeter. Example 1 83 parts of terephthalic acid, 377 parts of phenol, 12 parts of ethylbenzene, and 0.1 parts of tin acetate. was charged into a reactor equipped with a stirrer, a 1.5 TrL rectification column packed with a Raschig ring, and a cooler, and after purging the inside with nitrogen, the internal temperature was reduced to 290°C.
It was heated until.

The distilled liquid was separated into liquids and the upper layer of ethylbenzene was returned to the top of the rectification column.
After reacting for an hour, distilled water amounted to about 18 parts, so heating was stopped and the reactor was cooled. The contents cooled to 30°C and taken out were 52W).

From this, 100 parts were separated, the medium and excess phenol were expelled under vacuum at 240°C or less, and after drying, the acid value and color tone were measured. The acid value was 130 eq/1σy, and the b value was 3.0. It was hot. On the other hand, the reactant 10 taken out
0 parts were centrifuged and further rinsed with 50 m of ethylbenzene.

The obtained solid was dried under vacuum in the same manner as described above, and then 41.
3 parts, and the acid value of this product is 138 eq/1 (1 Py
The b value was 0.5. Comparative Example When the reaction was carried out under the same conditions as in Example 1 except that ethylbenzene was not used, only 5 parts of water came out after 3 hours.

When the reaction was further carried out while gradually lowering the internal pressure, the result was 6.5
17 parts of water was distilled off in 1 hour. An attempt was made to cool the reactant to 30° C. and take out the reaction product, but it solidified and was difficult to take out.

Claims (1)

[Scope of Claims] 1. In producing an aromatic dicarboxylic acid diaryl ester by reacting an aromatic dicarboxylic acid with an aromatic monohydroxy compound in an amount of 2.1 to 10 times the mole of the aromatic dicarboxylic acid, the reaction in the presence of an aromatic hydrocarbon having a boiling point of 105-175°C (under normal pressure) 230-350°C
1. A method for producing a diaryl ester, which is carried out by distilling off by-product water at a temperature of 0.degree. C., and then separating the reaction product from the aromatic hydrocarbon. 2 aromatic hydrocarbon to aromatic dicarboxylic acid.
The manufacturing method according to claim 1, characterized in that the amount is used in an amount of 1 to 10 times by weight. 3. The method according to claim 1 or 2, characterized in that the mixture of the reaction product and the aromatic hydrocarbon is cooled to 100° C. or lower, and the precipitated aromatic dicarboxylic acid diaryl ester is solid-liquid separated. Manufacturing method.