Polymerization solvent system recovery process in aramid fiber 1414 production

Abstract

The invention discloses a polymerization solvent system recovery process in aramid fiber 1414 production, and belongs to the technical field of high-molecular polymer production. In the technical scheme, through the work procedures of twice neutralization, twice pulping, extraction, steam stripping, refining and the like, para-aramid polymers are washed and purified; in addition, auxiliary agentsof calcium chloride and solvents of N-methyl pyrrolidone used in the production are recovered and are repeatedly utilized; the cyclic economy is formed; meanwhile, the chloride ion content in the discharged sewage is effectively reduced; the environment-friendly requirements are better met; and the environment-friendly and economic effects are achieved.

Description

technical field [0001] The invention relates to a process for recycling a polymerization solvent system in the production of aramid 1414, which is a recycling and environment-friendly process for washing aramid 1414 polymers and recovering a polymerization solvent system, and belongs to the technical field of high molecular polymer production. Background technique [0002] The full name of aramid 1414 is poly-p-phenylene terephthalamide, and it has become aramid II in China. Because of its high heat resistance, high tensile strength, high insulation, chemical corrosion resistance, high compressibility, high bending strength and high modulus, it is widely used in optical cables, tire cords, high-strength rigging , high-pressure container shells, automobile friction plates, construction geotechnical materials, various reinforced composite materials instead of steel, conveyor belts, special canvas and other fields; in the military, it is used to make bulletproof vests, helmets,...

AI Technical Summary

Problems solved by technology

[0004] This separation and purification process can recover most of the organic solvent NMP, and the recovery rate can reach more than 99.5%, and this process is also the most mature polymer washing and solvent recovery process route used in the industrial production of aramid fiber 1414, but the separation The disadvantage of the purification process is that during the washing, separation and extraction process, the extracted inorganic salts (CaCl 2 and NaCl) are difficult to recycle, and form wastewater with a chloride content of about 3%. Economical and extremely costly; on the other hand, for the directly discharged wastewater, the chloride content of 3% (30000mg / L) is very high, and chloride ions pollute the environment a lot. With the gradual increase of national environmental protection requirements, chlorine The emission requirements of ions are also gradually increasing, and this problem is becoming more and more prominent and needs to be solved urgently

[0007] 2. In the process of separating NMP and calcium chloride, the addition of halogenated alkanes, that is, the introduction of new substances into the washing system, and due to the porous nature of PPTA polymer resins, halogenated alkanes cannot be completely separated (among them, PPTA polymerized The impurity of the material resin is divided according to the mg / L level), and at the same time, this type of impurity will have a great impact on the subsequent spinning process, and the quality and output of the product will be affected;

[0008] 3. The solubility of calcium chloride in halogenated alkanes is low, and it is impossible to allow a large amount of calcium chloride to enter the liquid phase recovery system, resulting in too much residual calcium chloride in the solid phase, which will cause higher Concentrated chloride ions are discharged with sewage, affecting the environment (hydrogen chloride is the same);

[0009] 4. When the vacuum distillation of the halogenated alkanes washing liquid is carried out, if no new third material (such as water) is introduced, the temperature of the solvent recovery rectification tower will not be able to be effectively controlled, not only the halogenated alkanes can easily enter the tower still Decomposition and corrosion of equipment occurs, and there is a large amount of tar residue at the bottom of the still after rectification, and the yield and pass rate of solvent recovery are low, which is not conducive to large-scale industrial production

[0011] 1. It adopts one-step washing method, which only involves the removal of PPTA material impurities, but does not fully consider the environmental protection effect, that is, calcium chloride, hydrogen chloride, etc. cannot be effectively recycled, cannot reduce chloride ion emissions, and do not meet the increasingly stringent environmental protection requirements of the country;

[0012] 2. The space utilization rate is low and the space occupied is large, which is not conducive to equipment layout

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