New crystallization method of p-phenylenediamine

Abstract

A process for crystallizing p-phenyldiamine includes such steps as distilling p-phenyldiamine, dissolving in water, cooling while crystallizing, separation and vacuum drying. It features high purity and quality of product.

Description

Technical field: [0001] The invention relates to a method for purifying p-phenylenediamine. Specifically relates to a new crystallization method of p-phenylenediamine. Background technique: [0002] p-Phenylenediamine is a compound with a wide range of uses, widely used in cosmetics, dyes, rubber anti-aging agents, antioxidants, imaging agents, high-strength chemical fibers (aromatic), etc. [0003] The preparation of p-phenylenediamine generally adopts the reduction method of p-nitroaniline sodium sulfide, and the method of purification still uses the melt injection cooling method in the 1980s: the crude p-phenylenediamine enters the crystallization pot (device) after vacuum distillation ), let it stand for cooling, so that p-phenylenediamine solidifies into a solid, and then manually break the solid from the crystallization pot (device) and remove it, and then artificially divide it into white and gray according to the color of the solid. piece. Some products are ground...

AI Technical Summary

Problems solved by technology

It is difficult to isolate the air during such a long cooling process, so part of the p-phenylenediamine obtained from the crystallization pot (device) has been oxidized and turned red and black, and only a part of the center has not been oxidized to become genuine (white ), and during the cooling process of p-phenylenediamine, the molecular mobility is hindered, and it is difficult to form its own lattice

[0005] 2. The operating environment is poor and the labor intensity is high: the whole operation is done manually by manpower, and the p-phenylenediamine powder spreads during the crushing and crushing process, the operating environment is harsh, and it is harmful to the operator's body

[0006] 3. Waste of resources and low economic benefit: the current method generally has a white product (unoxidized) rate of about 50%, and the gray product can only be sold at a reduced price (about 5,000 yuan / ton) or re-steamed.

[0007] 4. Affect user use and product development: general users still need to pulverize massive p-phenylenediamine for use, but the powder will generate dust when feeding, which will cause harm; high-purity p-phenylenediamine (such as Fanglun, Imaging, etc.) products are not satisfactory in terms of quality

Flake p-phenylenediamine has been developed, that is, the melted body is rapidly cooled into flakes by a slicer before solidification, but the flakes fail to fundamentally improve product quality, and rapid cooling degrades and instabilizes product quality

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