JPS60199861A - Purification of aromatic diamine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for purifying aromatic diamines, and particularly to a method for removing coloring impurities contained in aromatic diamines.

Aromatic diamines are usually produced by the hydrogenation reaction of the corresponding aromatic nide compound, but in this reaction, various by-products are produced in addition to the desired product. Among these by-products, there are impurities that are the main cause of the product's color over time, or the amines will significantly color the product. Aromatic diamines, especially m- and p-phenylenediamine, are used as raw materials for heat-resistant polymers, so there is a strong demand for them to be less colored, but their removal is not easy. A law is proposed.

For example, a method in which an alkaline or acidic aqueous solution of amines is decolorized with activated carbon and then neutralized to precipitate crystals;
Methods such as adding zinc dust or acid chloride during distillation are known, but if the product is refined under harsh conditions and stored for a long period of time, for more than a month, it will become noticeably discolored.

In addition, many methods of preventing coloring using various additives have recently been proposed, but the addition of a third component is often disadvantageous from an industrial standpoint, and it is difficult to determine which method is appropriate. In addition, with these improvements, for example, sulfur, reducing sulfur compounds, etc. are added during distillation (Japanese Patent Laid-Open No. 49-31628), and sulfur dioxide gas (Japanese Patent Laid-Open No. 51-11722) is added to the distillation process. There are methods, but the additive itself is unstable, the operation is complicated due to problems with pollution, the environment, and equipment corrosion, and I-I equipment is required, so there are no satisfactory methods.
No. Furthermore, a method has been proposed in which aromatic diamine is extracted with water and xylene, etc., but this method requires an additional purification step and is complicated.

As a result of intensive studies aimed at improving these, the present inventors have found that by distilling aromatic cyamines or a mixture containing them in the presence of an inorganic base and/or its salt, aromatic diamines with good long-term stability can be produced. The present invention has been achieved by discovering that it is possible to obtain a similar type.

Examples of aromatic diamines applicable to the present invention include:
Examples include o-, m-1 or p-phenylenediamine, 1-lylenediamine, and isomer mixtures thereof.

In addition, as the inorganic base and/or its salt, NaOH,
KOH, Ca (OH) r, Na ICO*, K,
CO, etc., and particularly preferred are NatcOm and NaOH. The amount used may be 10 to 1,100 pp per crude phenylenediamine, but preferably 100 to 11,000 pp, and sufficient effects can be obtained by distilling under reduced pressure under commonly used conditions. Moreover, since the amount added is extremely small, there is no change during distillation due to the addition of the above-mentioned base.

The present invention will be specifically explained below with reference to Examples.

Example 1 Crude m-phenylenediamine sog obtained by catalytic hydrogenation of crude m-dinitrobenzene (O: 9.0%, M: 886%, P: 24%) according to a conventional method, Raw soda 0. After adding o25.9, 15 m
mtlg's ILJ, distilled under EC at 162C to produce almost colorless (colorless after solidification) fraction 482&? It's it. This fraction remained colorless even after being stored for 3 months in a room under a nitrogen blanket.

Comparative Example 1 Fractions 4B and 4& obtained by distilling Example 1 without adding caustic soda were almost colorless immediately after distillation, but after storage for 3 months under a nitrogen seal, they became blackish brown. was.

Example 2 Crude+lp obtained by catalytic hydrogenation of crude p-21heroaniline
p-phenylenediamine 50.9, soda carbonate (1
, +13 (17) was distilled under addition stage pressure to obtain 490 g of an almost colorless (white after solidification) fraction. This fraction did not change color over time even after being stored for one year at room temperature in a glass bottle in an air atmosphere. was not recognized.

Claims (1)

[Claims] A method for purifying aromatic diamines, which comprises distilling aromatic cyamines or a mixture containing them in the presence of an inorganic base and/or a salt thereof.