JPH0737431B2 - Method for producing dianilide terephthalic acid - Google Patents

Description

TECHNICAL FIELD The present invention relates to a process for producing dianilide terephthalic acid.

According to the method of the present invention, the target terephthalic acid dianilides can be produced in good yield.

The terephthalic acid dianilides are industrially useful substances such as a fluidity improver for thermoplastic resins such as polyphenylene ether resins (see, for example, JP-A-60-44547).

[Conventional technology]

It is already well known that, in general, dicarboxylic acid dianilides can be produced by reacting a corresponding dicarboxylic acid chloride with aniline. In addition, starting materials other than dicarboxylic acid chlorides, as to the production method of dicarboxylic acid dianilides, a method of mixing and heating a dicarboxylic acid and diphenyl urea (Chem.Abstr.) 899h (1955 )) And the like have been proposed, but in any case, a dicarboxylic acid chloride or an amidation reagent must be synthesized, which is not an industrially satisfactory method.

A method in which a dicarboxylic acid such as adipic acid and aniline are heated and condensed at 120 to 200 ° C. in the presence of a solvent (JP-A-61-2516).
Japanese Patent No. 49) is also proposed.

[Problems to be solved by the invention]

In the presence of the solvent, dicarboxylic acid and aniline
When the method of reacting at 120 to 200 ° C. and distilling the produced water out of the system by azeotropic distillation with a solvent is applied to terephthalic acid dianilides, the reaction progresses extremely slowly (see Comparative Example).
Furthermore, both the terephthalic acid dianilides produced and the raw material terephthalic acid have low solubilities in ordinary organic solvents, it is difficult to remove and purify the residual terephthalic acid, and terephthalic acid dianilides of high purity cannot be obtained.

The present invention is intended to solve the above problems and to provide a method for producing high-purity dianilide terephthalic acid in high yield.

[Means for solving problems]

The present invention provides a method for producing terephthalic acid dianilides, wherein (In the formula, R represents hydrogen, a C _1-15 alkyl group, an alkenyl group, or an aryl group), and
It is a process for producing dianilide terephthalic acid, which is characterized by reacting directly in a temperature range of 200 to 350 ° C.

The anilines used in the method of the present invention have the general formula (In the formula, R represents hydrogen, a C _1-15 alkyl group, an alkenyl group, or an aryl group).
For example, aniline, o-toluidine, m-toluidine,
p-toluidine, 2,4-xylidine, 3,4-xylidine,
4-n-butylaniline, 4-n-hexylaniline,
4-n-octylaniline, 4-n-decylaniline,
Examples include 4-n-decylaniline, 2,5-di-t-butylaniline, and 2,4,6-tri-t-butylaniline.

The molar ratio of terephthalic acid and anilines used as raw materials is 1/3
The range of to 1/20 is preferable, and the range of 1/5 to 1/15 is particularly preferable. When the molar ratio exceeds 1/3 and the amount of terephthalic acid increases, not only it becomes difficult to eliminate the raw material terephthalic acid, but the fluidity of the reaction mixture decreases as the reaction proceeds, It comes at a disadvantage in industrial practice. Further, when the molar ratio exceeds 1/20 and the amount of anilines is large, the amount of the reaction mixture becomes large, and the yield of the kettle is reduced, thereby deteriorating the economical efficiency, which is disadvantageous in industrial practice.

The reaction temperature is in the range of 200 to 350 ° C. The temperature is 200
When the temperature is lower than 0 ° C, the reaction rate is slow and it is difficult to practically eliminate the raw material terephthalic acid, and high-purity dianilide terephthalic acid cannot be obtained. Moreover, the temperature is
When the temperature is 350 ° C. or higher, the thermal deterioration of the anilines is remarkable, which causes coloring of the product, which is not preferable.

The reaction pressure may be atmospheric pressure or pressurized conditions, but when the boiling point of the aniline to be used is lower than or equal to the predetermined reaction temperature, an inert gas or the like is used so that the reaction mixture reaches the predetermined reaction temperature. It is sufficient to pressurize, and when the boiling point of the aniline is equal to or higher than the predetermined reaction temperature, there is no problem even if the reaction is carried out under normal pressure or under spontaneous pressure.

The reaction time varies depending on the reaction temperature and the molar ratio of the raw materials charged, and therefore cannot be uniformly specified. However, it is usually preferable to set the reaction time to 1 hour or more, but it is not necessary to unnecessarily extend the reaction time to prevent thermal deterioration of anilines. It is not preferred because it will occur.

As a specific method for carrying out the present invention, terephthalic acid and anilines are reacted under conditions of a predetermined temperature and pressure.

The obtained terephthalic acid dianilides have the general formula corresponding to the anilines used. (In the formula, R represents hydrogen, a C _1-15 alkyl group, an alkenyl group, or an aryl group). After completion of the reaction, the reaction mixture is cooled to crystallize terephthalic acid dianilides, and separated to obtain crude terephthalic acid dianilides. By washing this with lower alcohols such as methanol and ethanol, or aromatic hydrocarbons such as toluene, xylene, and ethylbenzene, white purified terephthalic acid dianilides can be obtained.

The liquid after crystallization of the desired product from the reaction mixture contains anilines, terephthalic acid, and terephthalic acid monoanilide, so this is recycled to the reaction step and reused as a raw material for terephthalic acid dianilide. Is possible.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1 16.6 g (0.1 mol) of terephthalic acid and 93 g (1.0 mol) of aniline were charged into a stainless steel autoclave with an internal capacity of 250 ml, and the inside of the reactor was replaced with an inert gas.
The mixture was heated and stirred at 280 ° C for 6 hours. After the reaction was completed, the reaction mixture was cooled to 40 ° C. or lower to precipitate crystals, which were then separated to obtain crude terephthalic acid dianilide. Toluene 10
After washing with 0 g at 50 ° C., it was separated and dried under reduced pressure to obtain 27.1 g of dianhydride of terephthalic acid (yield 85.9% (based on terephthalic acid charged)).

Examples 2 to 10 The same operations as in Example 1 were performed except that the anilines shown in Table 1 were used to obtain corresponding terephthalic acid dianilides. The results are shown in Table 1. Here, the yield of terephthalic acid dianilide refers to the amount (mol) of terephthalic acid produced (mol) with respect to the amount (mol) of charged terephthalic acid.

Comparative example terephthalic acid 33.2 g (0.2 mol), aniline 186.0 g (2.0
Mol) was charged into a three-necked flask with an internal volume of 300 ml, and the water produced was distilled out of the reaction system as an azeotrope with aniline, separated into an aniline phase and an aqueous phase, and then the aniline phase was circulated to the reaction system. When the reaction was carried out by the method
Even when heated at 5 ° C. for 6 hours, the produced water did not distill, and the reaction substantially did not proceed.

Claims (1)

[Claims] 1. Terephthalic acid and a general formula; (In the formula, R represents hydrogen, a C _1-15 alkyl group, an alkenyl group, or an aryl group), and
A method for producing dianilide terephthalic acid, which comprises reacting in a temperature range of 200 to 350 ° C.