JPH0549656B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing organic carboxylic acid chlorides. More particularly, the present invention relates to a simplified and economical method for producing high purity terephthalic acid chloride or isophthalic acid chloride of improved quality.

In recent years, carboxylic acid chloride has been used in heat-resistant resins, agricultural chemicals,
It has become industrially important as a raw material for medicines, etc.

A common method for producing this type of carboxylic acid chloride is to salt a carboxylic acid or anhydride with thionyl chloride, phosphorus pentachloride, phosphorus trichloride, phorphoryl chloride, or the like. Methods using phosgene have also been known for some time, but because they are much less reactive than the above-mentioned chlorinating agents, it is necessary to carry out the reaction under pressure or to use a catalyst. For this purpose, as catalysts, dimethylformamide (Japanese Patent Publication No. 10613, Showa 43), quaternary ammonium salts and phosphonium salts (Japanese Patent Publication No. 44, Showa 44) are used as catalysts.
27363), tetraalkylthiourea (Special Publication No. 1973-
27362), imidazole (Japanese Patent Publication No. 47-13021), and trimethylphosphine oxide (Japanese Patent Publication No. 1973-13021),
30821) etc. have been proposed.

Among these catalysts, lower aliphatic amides such as dimethylformamide are widely used because they have high activity, are relatively inexpensive, and are easily available.

However, it is known that the use of catalysts of this type produces tar-like products towards the end of the phosgenation reaction, often resulting in significant coloration of the final product.

Conventionally, as a method to solve this drawback, the obtained carboxylic acid chloride was heated at 180 to 280°C in the presence of sulfuric acid.
method of distilling after heat treatment (Japanese Patent Application Laid-Open No. 50-5346),
After the reaction is complete, aliphatic hydrocarbons such as n-hexane and n-heptane are added to the crude reaction product after removing the solvent used in the reaction as a solvent for precipitation of the catalyst and catalyst components such as tar derived from the catalyst. A purification method has been proposed in which the reaction product and the catalyst component are separated into layers after addition (Japanese Patent Application Laid-open No. 73720/1983).
These methods still require additional purification steps. Therefore, it is desired to find a method that does not require special purification steps and does not cause loss of catalyst components.

In view of the above circumstances, the present inventors conducted intensive studies to find a method for producing high-grade carboxylic acid chloride that does not require a special purification process and allows the recovery of the catalyst. In the method of producing the corresponding terephthalic acid chloride or isophthalic acid chloride by reacting acid or isophthalic acid or their intermolecular anhydrides with phosgene, if an aromatic hydrocarbon is used as the reaction solvent, the solvent can be removed after the reaction is completed. The layer containing the catalyst can be completely separated from the solvent layer containing the reaction products by simply leaving it to stand without washing.Moreover, this retains its catalytic activity, and the separated catalyst layer can be used for the next time as it is. The present invention was completed based on the discovery that high-grade carboxylic acid chloride can be reused in the phosgenation reaction, and that high-quality carboxylic acid chloride can be obtained by distilling the reaction solution after separation of the catalyst layer without any special purification treatment. I let it happen.

Examples of aromatic hydrocarbons used in the method of the present invention include benzene, toluene, xylene, ethylbenzene, kyumene, cymene, trimethylbenzene, diethylbenzene, diisopropylbenzene, ethyltoluene, tetralin, and the like.

The amount of catalyst used is generally 0.01 to 0.5 mol, particularly preferably 0.05 to 0.3 mol, per mol of carboxylic acid. If the amount of catalyst used is less than this, unreacted substances will remain, and if it is more than 0.5 mol, tar-like products will increase,
Separation and addition of a new catalyst are required. The amount to be used is appropriately determined depending on the reaction temperature. The reaction operating temperature is 30-100℃, especially 60℃
~90℃ is good. At temperatures below 30℃, unreacted substances remain;
When the temperature exceeds 100°C, the catalyst activity decreases significantly even if the separated catalyst layer is circulated, resulting in the frequent need to add a new catalyst.

Further, the reaction can be carried out continuously, semi-continuously, or batchwise.

According to the method of the present invention, the catalyst layer can be separated from the reaction mixture and can be reused, so it is extremely economical, and the reaction solution after separating the catalyst layer does not require any special purification operations, such as distillation etc. For example, a color number (APHA, hereinafter the same) measured by melting a product sample of 10 or less can be obtained.
The number of colors after heat resistance test (heating at 180℃ for 30 minutes or less) is 20 or less.

Next, examples of the present invention will be described.

Example 1 3.0 g (0.043 mol) of dimethylformamide as a catalyst, 99.7 g (0.60 mol) of isophthalic acid, and 99.7 g of toluene were added to a 300 ml four-necked flask equipped with a stirrer, a gas inlet tube, a thermometer, and a Dimroth condenser. After charging and stirring, phosgene was blown in at a rate of 30 g/hour, and the reaction was carried out at 70°C for 5 hours.

After the reaction was completed, the mixture was allowed to stand, and a brown oil layer containing the catalyst component separated in the lower layer, and the upper toluene layer was a homogeneous solution with a slight yellow tinge. After separating this catalyst layer, the toluene layer was distilled under reduced pressure to remove toluene. Subsequently distilled under reduced pressure,
121.0 g (yield 99.3%) of isophthalic acid chloride having a boiling point of 145-147°C/15-20 mmHg was obtained.

Freezing point of the obtained isophthalic acid chloride: 43.6
℃, the number of colors was 10 or less, and the number of colors for the heat resistance test product was 20.

Example 2 A reaction was carried out in the same manner as in Example 1, except that the brown oil layer containing the catalyst component separated from the reaction-completed liquid of Example 1 was used as it was in place of dimethylformamide.

The reaction was completed in 4.7 hours, and after being allowed to stand still, the lower oil layer containing the catalyst component was separated. The upper layer was subsequently subjected to vacuum fractional distillation to yield 120.8g of isophthalic acid chloride.
(yield 99.1%).

Freezing point of the obtained isophthalic acid chloride: 43.6
℃, the number of colors was 10 or less, and the number of colors for the heat resistance test product was 20.

The oil layer containing the catalyst component was recycled eight times in the same manner, but during this time there was no need to newly add dimethylformamide, and there was no change in the yield or quality of the product.

Comparative Example A reaction was carried out in the same manner as in Example 1 except that monochlorobenzene was used instead of toluene.

The reaction was completed in 5 hours. After the reaction was completed, most of the blackish brown tar-like product was dispersed in the solution even if it was allowed to stand still, and some of it was separated into an upper layer. After separating the liquid,
The lower layer was subjected to vacuum fractional distillation in the same manner as in Example 1 to obtain 120.7 g (yield 99.1%) of isophthalic acid chloride.

The freezing point of the obtained isophthalic acid chloride is 43.4
℃, the number of colors was 100, and the number of colors of the heated test product was 500 or more.

In addition, when the oil layer separated from the reaction mixture was recycled and reused, it took 8 hours to complete the reaction.
It was found that the catalyst loss was extremely large, and in order to keep the reaction time for each round under 5 hours and to recycle it, it was necessary to add 1/2 to 2/3 of the initial amount of dimethylformamide each time. Ta.

Example 3 The procedure was repeated in the same manner as in Example 1 except that terephthalic acid was used instead of isophthalic acid in Example 1, and the boiling point
Terephthalic acid chloride at 162-165℃/30mmHg
120.3g (yield 98.8%) was obtained. The freezing point was 81.6°C, the number of colors was 10 or less, and the number of colors in the heat resistance test was 20.

The oil layer containing the catalyst separated in this reaction was repeatedly used in subsequent reactions, and products with similar yield and quality were obtained.

Example 4 The reaction was carried out as in Example 1 except that toluene was o-xylene. The reaction took 5 hours. After the reaction was completed, the mixture was allowed to stand, and a brown oil layer containing the catalyst component was separated in the lower layer. The o-xylene layer after separating this catalyst was subjected to distillation as in Example 1,
121.1 g (yield 99.4%) of isophthalic acid chloride was obtained. The obtained isophthalic acid chloride was prepared in Example 1.
It had a freezing point of 43.6°C, the same as 43.6°C, a color number of 10 or less, and a heat resistance test product with a color number of 20.

The reaction was repeated using the brown oil layer containing the catalyst component in place of dimethylformamide.
The reaction was completed in 4.8 hours, and after being allowed to stand still, the lower oil layer containing the catalyst component was separated. The upper layer was subsequently concentrated and then distilled under reduced pressure to obtain 121.0 g (yield 99.3%) of isophthalic acid chloride. The obtained isophthalic acid chloride had a freezing point of 43.6°C, a color number of 10 or less, and a heat resistance test product with a color number of 20.

Example 5 The reaction was carried out as in Example 1 except that the toluene was diethylbenzene. The reaction took 5 hours.
After the reaction was completed, the mixture was allowed to stand, and a brown oil layer containing the catalyst component was separated in the lower layer. The diethylbenzene layer after separating this catalyst layer was treated as in Example 1 to produce 121.1 g of isophthalic acid chloride (yield: 99.4
%) was obtained. The obtained isophthalic acid chloride had a freezing point of 43.6° C., the same as in Example 1, a color number of 10 or less, and a heat resistance test product with a color number of 20.

The reaction was repeated using the brown oil layer containing the catalyst component in place of dimethylformamide.
The reaction was completed in 4.8 hours, and after being allowed to stand still, the lower oil layer containing the catalyst component was separated. The upper layer was subsequently concentrated and then distilled under reduced pressure to obtain 121.2 g (yield 99.5%) of isophthalic acid chloride. The obtained isophthalic acid chloride had a freezing point of 43.6°C, a color number of 10 or less, and a heat resistance test product with a color number of 20.

Example 6 The reaction was carried out as in Example 1 except that the toluene was tetralin. The reaction took 5 hours. After the reaction was completed, the mixture was allowed to stand, and a brown oil layer containing the catalyst component was separated in the lower layer. The tetralin layer after separating this catalyst layer was treated as in Example 1 to obtain 121.2 g (yield: 99.5%) of isophthalic acid chloride.

The obtained isophthalic acid chloride had a freezing point of 43.6° C., the same as in Example 1, a color number of 10 or less, and a heat resistance test product with a color number of 20.

The reaction was repeated using the brown oil layer containing the catalyst component in place of dimethylformamide.
The reaction was completed in 5 hours, and after standing still, the lower oil layer containing the catalyst component was separated. The upper layer was subsequently concentrated and distilled under reduced pressure to obtain 121.0 g of isophthalic acid chloride (yield:
99.3%). Freezing point of the obtained isophthalic acid chloride: 43.6℃, color number: 10 or less, color number of heat resistance test product:
It was 20.

Claims (1)

[Claims] 1 A method for producing a corresponding carboxylic acid chloride obtained by reacting terephthalic acid or isophthalic acid or an intermolecular anhydride thereof with phosgene in the presence of a lower aliphatic amide as a catalyst, in which aromatic carbonization is used as a reaction solvent. Hydrogen is used to convert lower aliphatic amides to carboxylic acids.
Using 0.01 to 0.5 mole times, react at 30 to 100°C,
After the reaction is completed, without removing the solvent used in the reaction, the oil layer is separated into an oil layer containing a catalyst component and an aromatic hydrocarbon solution containing a carboxylic acid chloride,
A method for producing terephthalic acid chloride or isophthalic acid chloride, characterized in that the separated aromatic hydrocarbon solution is directly subjected to distillation, and the oil layer containing the catalyst component is recycled and reused in the reaction system.