Process for recovering high-purity N-methyl formamide from waste stripping solution

Abstract

The invention relates to the technical field of waste stripping solution recovery, and provides a process for recovering high-purity N-methyl formamide from a waste stripping solution. The process includes rectifying the waste stripping solution containing N-methyl formamide and diethylene glycol methyl ether to obtain a NMF crude product having a mass concentration of 80-90%; repeating 1-3 timesof melting and crystallization; performing partial melting, melting, melt liquid collection and cooling for crystallization to obtain high-purity NMF. A technique combining melting and crystallizationwith rectification is adopted so that a problem that high-purity NMF cannot be obtained through recovery is solved, and the process has advantages of simple procedures, low investment, short period,a high yield and a low cost. The obtained high-purity NMF is high in purity which can be electronic chemical purity that is 99.99%, thus overcoming a problem that purity of a product of rectificationonly can reach 90%.

Description

technical field [0001] The invention relates to the technical field of recovery of waste stripping liquid, in particular to a process for recovering high-purity N-methylformamide from waste stripping liquid. Background technique [0002] The rapid development of the domestic electronics manufacturing industry has greatly increased the use of electronic chemicals such as strippers. In the production process of electronic components such as liquid crystal display panels and semiconductor integrated circuits, it is necessary to use a stripping solution to remove the photoresist coated on the microcircuit protection area as a mask. The stripping solution used is usually made of organic amine and polar organic A mixture of solvents, a mixture of N-methylformamide (NMF) and diethylene glycol methyl ether (MDG) is one of them. This group of solvents has a good effect after mixing, and the industrial usage has been increasing. However, the price is high, and it is difficult to reco...

AI Technical Summary

Problems solved by technology

The use effect of this group of solvents is good after mixing, and the industrial usage has been increasing, but the price is high, and it is difficult to recover high-purity products. If the waste liquid formed after use is directly discharged, it will cause environmental pollution and cause a great waste of resources.

[0003] The existing technology for recovering stripping liquid is mainly based on distillation technology, but what is recovered is often a mixed solvent, the product quality is low, and the use value is relatively low, so its use is greatly restricted

For the recovery of high-purity products of NMF and MDG, the group of waste stripping liquids, traditional rectification cannot separate this group of solvents, because the boiling point of NMF is 199°C, and the boiling point of MDG is 194°C. The boiling point difference is very close, and rectification requires a lot of time. High energy consumption can only extract up to about 90% of NMF, which cannot meet the purity requirements of high-purity electronic chemicals

At the same time, due to the high boiling point of this group of waste solvents, if industrialization is to be realized, high-vacuum system rectification is required. Even if the purity of 90% is to be achieved, the size of the rectification tower is also very large, which will greatly increase the investment in equipment

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