Poly-p-phenylene terephthamide (PPTA) polymer washing and solvent recovery method

Abstract

The invention provides a poly-p-phenylene terephthamide (PPTA) polymer washing and solvent recovery method. The method comprises the steps of washing a PPTA polymerization product by aliphatic halogen alkane, separating NMP (N-methyl-2-pyrrolidone) and part calcium chloride from the PPTA polymer in a washing way, and washing the PPTA polymer by water to obtain PPTA resin with high purity. The method has the advantages that the energy consumption is low, the water consumption is reduced, the wastewater treatment pressure is reduced, the purification efficiency is high, the halogen alkane washing solution can be directly circulated into a polymerization process for use, and the like.

Description

technical field [0001] The invention relates to a purification process of organic matter, in particular to a production technology for the purification of para-aramid fibers, specifically a method for washing polymers and recovering solvents in the production process of para-aramid fibers. Background technique [0002] Poly-p-phenylene terephthalamide (also known as aramid 1414 or para-aramid, referred to as PPTA) fiber is a high-strength fiber obtained by polycondensation in a low-temperature solution, washed and dried, then dissolved in concentrated sulfuric acid, and then dry-sprayed and wet-spun. High Modulus Fiber. Because there are a large number of benzene rings and amide structures in the PPTA molecular chain, the molecular chain is highly oriented along the length direction, the molecular chain is rigid, and has a strong inter-chain bonding force. The fiber obtained by dry-jet wet spinning has high strength, which is It is 5-6 times that of steel wire, light in wei...

AI Technical Summary

Problems solved by technology

The water obtained by this method of vacuum distillation can continue to wash the polymer, but due to the high boiling point of water and the large heat of evaporation, the energy consumption is high, and some calcium chloride crystals will block the pipeline during the desalination process, so continuous production cannot be performed. There is still a part of NMP in the residue after desalination, if it is not recovered, it will cause serious pollution to the environment

The second method is to process the washing waste liquid through multi-stage extraction to obtain the extract phase containing NMP and extraction solvent and the raffinate phase containing a large amount of water and calcium chloride. After the extractant in the extract phase is distilled out, the remaining NMP crude product is processed NMP is obtained by rectification for recycling. This method can reduce the energy consumption in the NMP recovery process, but if the raffinate phase is not processed afterward, it will be a large amount of industrial wastewater, and the pressure on environmental protection is very high.

If the raffinate phase is stripped, water can be recovered and reused, but this increases energy consumption

[0004] It can be seen from the above that the existing methods of washing para-aramid polymerization products need to use a large amount of industrial water, and the pressure on environmental protection is high. If the waste water after washing is recovered, the energy consumption in the recovery process will be relatively large.