JPS6313976B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing organic carboxylic acid chlorides. Furthermore, the present invention relates to a method for producing high-purity carboxylic acid chloride with improved quality.

In recent years, carboxylic acid chlorides have become industrially important as raw materials for heat-resistant resins, agricultural chemicals, medicines, and the like.

A common method for producing this type of carboxylic acid chloride is to salt a carboxylic acid with thionyl chloride, phosphorus pentachloride, phosphorus trichloride, phosphoryl chloride, or the like. A method using phosgene has also been known for some time, but it has the drawback of being less reactive than the above-mentioned chlorinating agents.

However, in recent years, with the development of the urethane industry, phosgene has been produced in large quantities and has become more economically available than thionyl chloride, etc., and various catalysts have been proposed to increase the reactivity when using phosgene. For example, dimethylformamide (Special Publication No. 43-
10613), quaternary ammonium salts and phosphonium salts (Japanese Patent Publication No. 44-27363), tetraalkylthiourea (Japanese Patent Publication No. 44-27362), imidazole (Japanese Patent Publication No. 47-1989)
13021) or trimethylphosphine oxide (JP-A-50-30821) is known to be used as a catalyst.

Among these catalysts, lower aliphatic amides such as dimethylformamide have excellent activity, are inexpensive and easily available, and are common.

However, a serious drawback when using catalysts of this type is that their decomposition, polymerization, etc. give rise to tar-like products, which often lead to a marked discoloration of the product. Even if the reaction product is distilled, trace amounts of impurities will be mixed into the product, and the product will be colored and change over time, making it unsuitable for applications that require high quality.

The present inventors have conducted intensive studies on a method for producing high-quality carboxylic acid chloride with excellent hue and good stability over time.
We believe that this objective can be achieved by an industrially extremely easy method of adding one or more metals selected from Cr, Mn, Fe, Co, and Ni or their compounds, followed by heat treatment and distillation. Heading: The invention has been completed.

That is, the present invention relates to a method for producing a corresponding carboxylic acid chloride by reacting a carboxylic acid with phosgene in the presence or absence of an inert solvent using a lower aliphatic amide as a catalyst, in which a solvent is used in the reaction product or In this case, the concentrated liquid or crude product obtained by removing part or all of the solvent from the reaction product liquid,
Or, one or more metals or compounds thereof selected from the above metal group are added to the distillate thereof, and the temperature is increased to 70 to 200°C, preferably 120 to 180°C.
This is a method for producing a carboxylic acid chloride of excellent quality, which is characterized by carrying out heat treatment and distillation at a temperature of 1,000,000,000, preferably under an inert gas atmosphere.

Examples of compounds of the metal group used in the method of the invention include the respective chlorides, bromides, iodides, oxides, sulfides, nitrates, sulfates, hydroxides, carbonates, acetates and other organic acids. Examples include salt.

Examples of carboxylic acids that can be used in the present invention include aliphatic carboxylic acids such as acetic acid, propionic acid, and butyric acid, aromatic carboxylic acids such as benzoic acid, phthalic acid, tetrahydrophthalic acid, terephthalic acid, isophthalic acid, and trimellitic acid, and cyclohexane. Examples include alicyclic carboxylic acids such as carboxylic acids.

When a solvent is used in the phosgenation reaction, any known solvent may be used, such as benzene, toluene, xylene, monochlorobenzene,
Examples include dichlorobenzene and ethyl acetate. The amount of catalyst in the phosgenation reaction is 0.01 to 0.5 mol, especially 0.05 to 0.3 mol per mol of carboxylic acid.
Mole is good. The reaction temperature is preferably 30 to 100℃, especially
50-90℃ is good. At temperatures below 50°C, the reaction time becomes longer, and at temperatures above 90°C, tar-like products tend to increase.

The heat treatment of the method of the present invention can be carried out by using the phosgenation reaction solution obtained in this way as it is, or when using a solvent, removing part or all of the solvent to obtain a concentrated solution or a crude product, or distilling them to obtain a crude product. This is done for distilled products.

The amount of metal or metal compound added will vary depending on the amount of impurities in the refined raw materials, processing conditions, etc.
0.001-1.0% is sufficient.

The heat treatment temperature is usually 70° to 200°C, especially 120° to
180°C is preferred. The required treatment time depends on the heating temperature, but heating for 5 hours at 120°C and 1 hour at 180°C is sufficient.

The purified product obtained by this treatment has a significantly superior hue compared to that obtained by distillation without any treatment. (Heat for 30 minutes)
The number of colors after that is 20 or less.

Next, examples of the present invention will be described.

Example 1 5.0 g (0.07 mol) of dimethylformamide and 166.5 g (1.0 mol) of terephthalic acid were mixed with 390 g of o-dichlorobenzene, and 60 g of phosgene was added at 90°C.
The reaction was carried out for 4 hours by blowing at a rate of g/hour.
Excess phosgene was removed by passing nitrogen gas through the reaction solution at a rate of 40/hour for about 1 hour at the same temperature. The catalytic active component turned into tar, and the reaction solution was colored brown. O-dichlorobenzene was distilled off from this reaction solution to obtain 200.3 g of a dark brown crude product.

1.0 g of iron chloride was added to this crude product, heat treated at 180° C. for 1 hour while passing nitrogen (approximately 10/hour), and then distilled under reduced pressure. The obtained purified terephthalic acid chloride weighed 198.8g (yield 98.0%), and had a color number of 10 when melted.
Number of colors after heat resistance test: 20, purity: 99.8%, freezing point: 81.6℃
It was hot.

Example 2 Except for replacing terephthalic acid with isophthalic acid,
Phosgenation and heat treatment were carried out as in Example 1.

Distilled under reduced pressure to produce purified terephthalic acid chloride 197.6g
(yield 97.4%). The number of colors when melted is 5 or less, the number of colors after heat resistance test is 10 to 20, the purity is 99.8%,
The freezing point was 43.6°C.

Example 3 Phosgenation and heat treatment were carried out as in Example 1 except that nickel chloride was used instead of iron chloride.

198.7g of purified terephthalic acid chloride by vacuum distillation
(yield 98.0%). Number of colors when this thing melts
10, Number of colors after heat resistance test: 30, purity: 99.7%, freezing point
It was 81.6℃.

Example 4 Phosgenation and heat treatment were carried out as in Example 1, except that 200 g (1.0 mol) of lauric acid was used instead of 166.5 g (1.0 mol) of terephthalic acid.

Distillation was carried out under reduced pressure to obtain 210.0 g (yield 96.0%) of lauric acid chloride.

Number of colors for this item is 10 or less, number of colors after heat resistance test is 10 or more
20, purity was 99.8%.

Example 5 The same procedure as in Example 1 was carried out, and o-dichlorobenzene was distilled off from the phosgenation reaction solution, followed by vacuum distillation. Distilled products have over 500 colors and are 94.5% pure.
It was hot. Add 1.0g of iron powder to this and heat it at 120℃ for 5 minutes.
The color number of the product obtained by redistilling after heat treatment in a nitrogen atmosphere is 10, and the color number after heat resistance test is 30, and the purity is
It was 99.8%.

Claims (1)

[Claims] 1. In a method for producing a corresponding carboxylic acid chloride by reacting an organic carboxylic acid with phosgene using a lower aliphatic amide as a catalyst in the presence or absence of a solvent, One or two selected from Zn, Ti, V, Cr, Mn, Fe, Co, and Ni are added to the concentrate or crude product obtained by removing part or all of it, or to the distillate thereof. A method for producing high-purity carboxylic acid chloride, which comprises adding the above metals or their compounds, heating them, and then distilling them.