Method for removing low-boiling-point impurities in polypropylene glycol monomethyl ether

Abstract

The invention discloses a method for removing low-boiling-point impurities in polypropylene glycol monomethyl ether. Multiple stages of cross-flow evaporators, which sequentially communicate with each other, are used for flash evaporation removal: a vapor guide pipe and an overflow pipe are uniformly distributed inside each stage of cross-flow evaporator, the vacuum degree and temperature are controlled and set, the polypropylene glycol monomethyl ether raw solution is added from the primary cross-flow evaporator on the top, the raw material addition amount is controlled, the raw material transversely flows in each stage of cross-flow evaporator, flows into the next stage of cross-flow evaporator through the overflow pipe, and finally flows to the kettle bottom; vapor formed by each stage of cross-flow evaporator is guided into the previous stage of cross-flow evaporator through the vapor guide pipe, guided into a condenser via a vacuum tube to be cooled, and is absorbed by water in a collecting flask; and aldehyde and methanol in the vapor are absorbed by the water, thereby obtaining the treated polypropylene glycol monomethyl ether on the tower bottom. Compared with the traditional technique, the method disclosed by the invention can effectively control the temperature of each stage of flash evaporation process, shortens the time of the impurity removal process, and ensures the MPPG400 chroma to be colorless.

Description

technical field [0001] The invention discloses a method for removing low-boiling point impurities in polypropylene glycol monomethyl ether, in particular to a multistage cross-flow flash evaporator, a temperature control system and an evaporation system for removing trace formaldehyde in polypropylene glycol monomethyl ether , acetaldehyde, methanol and water. Background technique [0002] Polyalcohol ether is a class of fine chemicals with a wide range of uses. As a good solvent, it is widely used in coatings, inks, printing and dyeing and cleaning agents. It can also be used as an additive for brake fluid and aviation fuel, because 99.9% The above propylene glycol ethers are basically non-toxic and are replacing the widely used but highly toxic polyethylene glycol ethers, especially in the textile printing and dyeing industry and the daily chemical industry, and are widely used as thickeners, lubricants and plasticizers. [0003] There are many types of polypropylene glyc...

AI Technical Summary

Problems solved by technology

In the above process, due to the addition of polypropylene glycol and methanol containing aldehyde and high water content, the finished product of polypropylene glycol methyl ether contains high aldehyde, methanol and water, and has a certain odor, which affects the performance of MPPG400 in food plastic products and daily necessities. application

In the past, the gap decompression flash method and vacuum distillation method were mainly used to remove aldehydes, methanol and water. The residence time is short and the removal is not complete. After the polypropylene glycol monomethyl ether is treated by the above method, the aldehyde value, methanol content and water can reach 7ppm, 0.1% and 0.4% respectively, but it is difficult to achieve the aldehyde value ≤ 1.0ppm and the methanol content ≤0.01%, water content ≤0.04%, and colorless and odorless

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