JPS62111942A - Production of 3,4,5,6-tetrafluorophthalic acid - Google Patents

Abstract

PURPOSE:To obtain the titled compound safely and in high yield, by converting 3,4,5,6-tetrafluoronitrile in a highly concentrated aqueous solution of sulfuric acid at low temperature into an intermediate reaction product having low volatility, diluting the reaction into a desired sulfuric acid concentration and carrying out hydrolysis. CONSTITUTION:3,4,5,6-Tetrafluorophthalic acid is reacted in >=75wt%, preferably >=85wt% highly concentrated aqueous solution of sulfuric acid at preferably 20-130 deg.C to give an intermediate reaction product comprising mainly 3,4,5,6- tetrafluorophthalimide, which is hydrolyzed in an aqueous solution of sulfuric acid having low concentration, preferably 35-75wt% at 90-170 deg.C to give 3,4,5,6- tetrafluorophthalic acid. USE:An intermediate for polymer material, drugs or agricultural chemicals.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention provides the following method: 3.4,5.6-titrafluorophthalonitrile is hydrolyzed in an aqueous solution of 1iii1i acid;
The present invention relates to a method for industrially producing 4,5.6-tetrafluorophthalic acid.

3.4,5.6-Te1-Raful A phthalic acid is useful as a polymer material, a pharmaceutical, an agricultural mulberry intermediate, and the like.

(Prior art) A method for producing 3,4,5,6-tetrafluorophthalic acid by hydrolyzing 3,4,5,6-te1-rafluorophthaloni-1-lyl in an aqueous sulfuric acid solution is as follows: It is described in Ishikawa et al., Industrial Chemistry Journal, Vol. 73, p. 447 (1970). According to this method, 80a of 3,4,5,6-titrafluorophthalonitrile is dissolved in 500% of a 60% aqueous sulfuric acid solution.
After boiling in Idl for 5 hours, the precipitated crystals were filtered, washed with 18% hydrochloric acid, and dried.
4,5.6-Te1-rafluorophthalic acid was obtained (yield 88.5%).

(Problems to be Solved by the Invention) However, according to the method described in the above-mentioned document, 3,4,5,6-te1-rafluorophthalonitrile is simply added to an aqueous sulfuric acid solution having a concentration of 60% by weight. When attempting to produce 3,4,5,6-te1-rafluorophthalic acid by hydrolysis with
~ Rafluorophthaloni I ~ Ryl (m, 0° 87°C) when the temperature of the reaction solution is raised (50°C or higher) or unreacted 3.4,
A phenomenon is observed in which a large amount of 5.6-titrafluorophthalonitrile sublimes at the initial stage of the reaction when a large amount remains, and adheres as a solid to a cold place, such as a condenser. If such a phenomenon occurs, there is a risk that the condenser will become clogged and pressurized. Therefore,
The purpose of the present invention is to prevent sublimation troubles of 3,4,5,6-Te1helafluorophthalonitrile as a starting material when hydrolyzing the material in an aqueous sulfuric acid solution, and to use the 1J method, which is industrially non-hazardous. And, the yield is good < 3.4, 5.6
-Producing putraflu 1-17 taric acid.

(Means for Solving the Problems) The present inventors developed the method described in 3.4 in an aqueous sulfuric acid solution. ! i, 6--7
When producing 3.4,5.6--1i-rafur A phthalic acid by hydrolyzing 1-rafluorophthaloni-1-ryl■, 3.4,5.6-te1-ranol/1' Various studies have been conducted on a method for producing 3.4,5.6-tetrafluorophthalic acid in a good yield with almost no risk of clogging the apparatus due to sublimation of [1phthaloni]-lyl.

To bind them together, firstly, in a highly concentrated sulfuric acid aqueous solution at low temperature, 3.
4,5,6-Titrafluor['] Phthaloni-1-lyl is replaced with an intermediate product with low sublimability (mainly 3,4,5,6-Titraflu A phthalimide), diluted to the specified concentration of sulfuric acid for invasion, and added with water. The inventors have discovered that the above-mentioned dangers can be avoided by decomposition, and that the desired 3,4,5,6-te1-helafluorophthalic acid can be produced industrially in high yields, and the present invention has been completed. Ta.

That is, the present invention is specified as follows.

(113,4,5,6-te1~rafluorophthaloni l
~When producing 3,4,5,6-tetrafluorophthalic acid by hydrolyzing lylu, first, 3,4,5,6-titrafluor A is reacted in a high-temperature aqueous sulfuric acid solution of 75% by weight or more. 3,4,5,6-titrafluoro I, which is characterized by obtaining an intermediate product mainly consisting of loftalimide, and then hydrolyzing the intermediate product in a low-temperature aqueous sulfuric acid solution.
] Phthalic acid production method.

(2) The reaction to produce an intermediate product mainly consisting of 3,4,5,6-tetrafluorophthalimide is carried out in an 85% by weight or more sulfuric acid aqueous solution at a temperature range of 20 to 130°C. The manufacturing method described in (1) above.

(3) 3.4,5.6-The reaction to hydrolyze an intermediate product mainly containing fluorophthalimide is 35
(1) or (1) above, characterized in that it is carried out in a ~75% by weight aqueous sulfuric acid solution at a temperature range of 90~170°C.
2) The method described.

Hereinafter, specific embodiments of the present invention will be explained. First, 3.4,
3.4,5 from 5.6-titranorophthalonitrile
．． A company that produces intermediate products mainly composed of 6-tetrafluorophthalimide! 1 will be explained.

According to the findings of the present inventors, this reaction can be achieved in good yield by performing it in a high temperature aqueous sulfuric acid solution. Especially f
The acidity is preferably 75% by weight or more, more preferably 85% by weight or more, and the reaction temperature is 2.
A temperature of 0 to 130°C, preferably 50 to 100°C is employed. Even during the reaction for producing this intermediate product, sublimation of the above-mentioned 3,4,5,6-titrafluorophthalonitrile may occur, so measures must be taken to prevent this. That is, in order to prevent sublimation, it is advantageous to carry out the reaction at the lowest possible temperature in a high-temperature sulfuric acid aqueous solution. Furthermore, since this reaction is an exothermic reaction, it is preferable to avoid carrying out the reaction in highly concentrated sulfuric acid and at high temperatures as it is dangerous. The wood inventors found that even under such reaction conditions, melting 1! 3.4,5.6-titraflu first lid of the reduced raw material was added to an aqueous tolylic acid solution to carry out the reaction.
Although the reaction time is short, we have discovered an excellent reaction method that prevents the risk of sudden heat generation and virtually no sublimation of unreacted 6-phthalonitrile. . However, 3.4.5,
6-'':i:'Draflu A When producing an intermediate product mainly consisting of phthalimide, sulfuric acid at a predetermined concentration and 3,4,5,6-tetrafluorophthalonitrile as a raw material are simultaneously charged into a reactor and reacted. Even if reaction method 1 is selected within the range described in 2 above, no problem will arise.

In this reaction, 3,4,5,6-te1-rafluorophthalimide is mainly produced, but in addition, acid amide compounds or 3,4,5,6-te1-rafluorophthalonyl and sulfuric acid are also produced. ] Intermediate products such as embrex are formed, and these do not sublimate even if the reaction temperature is increased, and are the target products in the next step 3 , 4 , 5
, 6-7-1 is converted to lafluorophthalic acid. Further, during this reaction, a part of 3,4,5,6-te1-hephthalimide may be hydrolyzed to 3,4,5,6-tetrafluorophthalic acid. Thus, through this reaction, most of the raw material tetrafluorophthalonitrile is converted to an intermediate product, 3,4,5.6--r trafluoro[]phthalic acid1! It's closed.

The reaction type is 3,4,5.6-teh dissolved in sulfuric acid.
Rahul A Lofta [Conil 1~Ryl may be added dropwise in small amounts, or J, , and the specified sulfuric acid and 3.4, 5.
6-'y-I HERAFUL A LONOTA [l After charging nitrile/V at the same time, the reaction may be carried out by keeping the arms warm. The reaction time is not particularly limited, but is in the range of 0.2 to 24 hours, especially 1=1
It is desirable to carry out the test within the range of 0 hours. After forming the intermediate in the first stage, the reaction solution is diluted with water to adjust to a predetermined m degree of sulfuric acid, and then the reaction is carried out.
5.6-te1~rafluorophthalic acid is obtained, but the sulfuric acid concentration in the aqueous medium in this second stage is 20 = 75% by weight
It is best to carry out the concentration in the range of 35 to 6.
A range of 5% crushing is good. When the concentration of sulfuric acid is high, a rapid reaction tends to occur, which is dangerous due to exothermic reaction. When the sulfuric acid concentration is low, the reaction rate decreases and productivity decreases, which is not preferable. Therefore, it is necessary to select an appropriate sulfuric acid concentration.

The reaction temperature for hydrolysis is preferably selected in the range of 90 to 170°C, particularly preferably in the range of 100 to 150°C.

If the reaction temperature is high, a rapid reaction occurs and is dangerous due to exothermic reaction. If the reaction temperature is low, the reaction rate decreases and productivity decreases, which is not preferable.

The reaction temperature is particularly controlled by the sulfuric acid concentration when carried out under reflux, but it is preferable to carry out the reaction under ring sulfur. However, the process may be carried out under pressure using an autoclave so that the temperature is not controlled by the sulfuric acid concentration, and even if the process is carried out at normal pressure, it is not necessarily necessary to carry out the process under reflux, and it may be carried out by controlling the temperature to an even lower temperature. good.

There is no particular restriction on the reaction time, but the reaction time is 5 to 40 hours.
4,5.6-Tetrafluorophthalic acid production method", a convenient treatment method after the completion of the reaction was presented, but these methods can also be applied to the present invention. Therefore, based on these, after the reaction is completed, the sulfuric acid concentration in the aqueous medium is approximately! , 37% by weight or more, preferably 20-57% by weight if diluted with water.

After the reaction is completed, Schiff maintains the sulfur R concentration as specified in 1-, and adjusts the liquid temperature to 0 to 40°C, preferably 10 to 35°C. 3.4, 5.6 A precipitate of -Te1-rafluorophthalic acid is obtained, which can be removed from the aqueous medium by means such as filtration, which is a common method.

Thus obtained 3, lI, 5. The crystals of G-tetrafluorophthalic acid contain water, so sulfuric acid,
A small amount of ammonium sulfate also remains.

The method for refining them -C is 3.4,
There is a method to remove sulfuric acid and VA acid ammonium by washing with a saturated or nearly saturated aqueous solution of 5.6-titraflu A1 phthalic acid. Washing may be performed using water at a temperature of 15° C. or lower, at which the solubility in water decreases rapidly. In this case, a part of the washed aqueous solution can be used as the aqueous medium for the reaction; or as the dilution water referred to in the present invention. is effectively recovered again.

Yet another method is to use 3.4, 5. This is a method for extracting Ci-tetrafluorophthalic acid. After extraction, the solvent is removed by evaporation to dryness, and 3,4,5,6-te1-lanorolonotaric acid can be taken out.

In the present invention, any method may be used for purification, but in some cases, the product may be used as it is as a raw material for the next reaction without being purified.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited thereto.

Example 1 1. J! , 200.1 (1,00 mol) of 3,4,5,6-titrafluorophthalonitrile and 473.7 g (4,69-
The mixture was charged with a mixture of 100 and 200 ml and reacted at 70'C for 2 hours with stirring. After the reaction was completed, a portion of the reaction solution was extracted with ether, and then analyzed using gas chroma 1 to graphite.3, 4, 5.
It was found that 3,4,5,6-detraflu A[]phthalimide was mainly formed as the peak of 6-te1~rahul A lophthalonyl l-lyl was not observed.

Next, these reaction solutions were diluted with 377 grams of water to adjust the sulfuric acid concentration to approximately 54% by weight, and then the stomach was exhausted and the solution was refluxed (approximately 128 grams).
The reaction was allowed to proceed for 1/1 hour while stirring at a temperature of 1/25°C.

After the reaction was completed, 127 g of water was added dropwise to dilute the reaction mixture to reduce the value to about 1% MIA degree/17 crj-ff.

After cooling (liquid temperature: 20°C), the white precipitate was filtered and separated from the aqueous medium.

3.4,5.6-11 were washed with a saturated aqueous solution of Rahul A phthalic acid and then dried to give 3,4,5.6-detranorophthalic acid 23),1(1(vs. 3,4 ,5.6-
Tetrafluorophthalonitrile yield! 17. FEE%
) could be obtained.Example 2 211. The reaction solution was then diluted with 547.6 g of water to adjust the concentration to about 45% protein content, and
3. The same procedure as in Example 1 was carried out except for the time reaction.
229.2 g of 4,5.6-tetrafluorophthalic acid (
A yield of 96.3 mol % for 3,4,5.6-titrafluorophthalonitrile was obtained.

Example 3 528.29 (4.69 mol) of 87% by weight sulfuric acid was charged to form an intermediate, and the reaction solution was then diluted with 2 mol of water.
The procedure was repeated in the same manner as in Example 1, except that the sulfuric acid concentration was adjusted to about 60% by weight, and the reaction was carried out under reflux for 12 hours.
0 (yield of 96.8 mol % based on 3,4,5.6-titrafluorophthalonitrile).

Claims (3)

[Claims] (1) When producing 3,4,5,6-tetrafluorophthalic acid by hydrolyzing 3,4,5,6-tetrafluorophthalonitrile, first, in a highly concentrated sulfuric acid aqueous solution of 75% by weight or more, A 3,4,5, Method for producing 6-tetrafluorophthalic acid. (2) The reaction to produce an intermediate product mainly consisting of 3,4,5,6-tetrafluorophthalimide is carried out in an 85% by weight or more sulfuric acid aqueous solution and at a temperature range of 20 to 130°C. The manufacturing method according to claim (1), characterized by: (3) The reaction of hydrolyzing the intermediate product mainly consisting of 3,4,5,6-tetrafluorophthalimide is carried out in a 35-75% by weight aqueous sulfuric acid solution and at a temperature range of 90-170°C. The method according to claim (1) or (2), characterized in that: