Method for recycling solvent during poly-para-phenylene terephthalamide reaction

Abstract

The invention relates to a method for recycling a solvent during poly-para-phenylene terephthalamide reaction, and belongs to the technical field of synthesis of high-molecular materials. The poly-para-phenylene terephthalamide prepared through polycondensation at a low temperature is washed to obtain an NMP (N-Methylpyrrolidone) and calcium chloride water solution, and the NMP and calcium chloride water solution passes through a filtering system, a dewatering system, a coarse distillation system, a preparation system, a fine distillation system, and the like to obtain an NMP-calcium chloride solution with water ratio less than 150 ppm. The method disclosed by the invention reduces the operating temperature and enhances the solution purity by adding an auxiliary agent to the coarse distillation system, obtains an NMP-calcium chloride system capable of being recycled in a polymerization unit through the preparation system and solves the problem of recycling of calcium chloride.

Description

technical field

[0001] The invention relates to a solvent recycling method in the reaction of poly-p-phenylene terephthalamide, belonging to the technical field of polymer material synthesis. Background technique

[0002] Poly-p-phenylene terephthalamide (PPTA) is a high-performance engineering material, and hexamethylphosphoramide, dimethylacetamide, N-methylpyrrolidone and tetramethylurea can be used in the synthesis process As a solvent, among them N-methylpyrrolidone (NMP) is widely used. NMP is expensive. In the synthesis process, NMP is used in a large amount and has strict requirements (such as requiring moisture content <150ppm, etc.). Therefore, solvent recycling is one of the key factors to reduce the cost of PPTA and industrialize it. In the process of synthesizing PPTA, calcium chloride is often used as co-solvent, however, the recycling of calcium chloride is still an unsolved problem.

[0003] As far as the applicant knows, the Chinese patent with applicat...

Examples

Embodiment 1

[0018] In this embodiment, the solvent is recycled through the following steps: add calcium hydroxide to the washing solution to obtain a neutralizing solution with pH=7, pass the neutralizing solution through a bag filter with a filtration accuracy of 5um, and collect the filtrate in a storage tank , Send the filtrate to the dehydration system for dehydration by vacuum distillation. The distillation parameters are absolute pressure 2KPa and temperature 70°C. The dehydration system can remove most of the water. Then add 2% ethanol additive to the solution, and send the solution into the crude distillation system, control the absolute pressure in the crude distillation tower to 3KPa, the temperature is 90°C, and the water content in the solution after crude distillation is <0.5%. Add anhydrous calcium chloride to the solution after crude distillation to obtain a solution with a calcium chloride concentration of 0.13 mol / L, and input the solution into a rectification tower with a...

Embodiment 2

[0020] In this embodiment, the solvent is recycled through the following steps: adding calcium carbonate to the washing solution to obtain a neutralizing solution with pH=7, passing the neutralizing solution through a tubular filter with a filtration accuracy of 3um, collecting the filtrate in a storage tank, The filtrate is sent to the dehydration system for vacuum distillation and dehydration. The distillation parameters are an absolute pressure of 3KPa and a temperature of 90°C. Then add 0.5% ethanol-methanol additive to the solution, and send the solution into the crude distillation system, control the absolute pressure in the crude distillation tower to 2KPa, the temperature is 100°C, and the water content in the solution after crude distillation is <0.3%. Add anhydrous calcium chloride to the solution after crude distillation to obtain a solution with a concentration of calcium chloride of 0.15 mol / L, and input the solution into a rectification tower with an absolute pres...

Embodiment 3

[0022] In this embodiment, the solvent is recycled through the following steps: add calcium hydroxide to the washing solution to obtain a neutralizing solution with pH=7, pass the neutralizing solution through a bag filter with a filtration accuracy of 2um, and collect the filtrate in a storage tank , the filtrate is sent to the dehydration system for dehydration by vacuum distillation, the distillation parameters are an absolute pressure of 4KPa and a temperature of 80°C. Then add 1% methanol additive to the solution, and send the solution into the crude distillation system, control the absolute pressure in the crude distillation tower to 1KPa, the temperature is 80°C, and the water content in the solution after crude distillation is <0.8%. Add anhydrous calcium chloride to the crude distillation solution to obtain a solution with a calcium chloride concentration of 0.17 mol / L, and input the solution into a rectification tower with an absolute pressure of 0.8KPa and a temperat...

technical field

[0001] The invention relates to a solvent recycling method in the reaction of poly-p-phenylene terephthalamide, belonging to the technical field of polymer material synthesis. Background technique

[0002] Poly-p-phenylene terephthalamide (PPTA) is a high-performance engineering material, and hexamethylphosphoramide, dimethylacetamide, N-methylpyrrolidone and tetramethylurea can be used in the synthesis process As a solvent, among them N-methylpyrrolidone (NMP) is widely used. NMP is expensive. In the synthesis process, NMP is used in a large amount and has strict requirements (such as requiring moisture content <150ppm, etc.). Therefore, solvent recycling is one of the key factors to reduce the cost of PPTA and industrialize it. In the process of synthesizing PPTA, calcium chloride is often used as co-solvent, however, the recycling of calcium chloride is still an unsolved problem.

[0003] As far as the applicant knows, the Chinese patent with applicat...

Examples

Embodiment 1

[0018] In this embodiment, the solvent is recycled through the following steps: add calcium hydroxide to the washing solution to obtain a neutralizing solution with pH=7, pass the neutralizing solution through a bag filter with a filtration accuracy of 5um, and collect the filtrate in a storage tank , Send the filtrate to the dehydration system for dehydration by vacuum distillation. The distillation parameters are absolute pressure 2KPa and temperature 70°C. The dehydration system can remove most of the water. Then add 2% ethanol additive to the solution, and send the solution into the crude distillation system, control the absolute pressure in the crude distillation tower to 3KPa, the temperature is 90°C, and the water content in the solution after crude distillation is <0.5%. Add anhydrous calcium chloride to the solution after crude distillation to obtain a solution with a calcium chloride concentration of 0.13 mol / L, and input the solution into a rectification tower with a...

Embodiment 2

[0020] In this embodiment, the solvent is recycled through the following steps: adding calcium carbonate to the washing solution to obtain a neutralizing solution with pH=7, passing the neutralizing solution through a tubular filter with a filtration accuracy of 3um, collecting the filtrate in a storage tank, The filtrate is sent to the dehydration system for vacuum distillation and dehydration. The distillation parameters are an absolute pressure of 3KPa and a temperature of 90°C. Then add 0.5% ethanol-methanol additive to the solution, and send the solution into the crude distillation system, control the absolute pressure in the crude distillation tower to 2KPa, the temperature is 100°C, and the water content in the solution after crude distillation is <0.3%. Add anhydrous calcium chloride to the solution after crude distillation to obtain a solution with a concentration of calcium chloride of 0.15 mol / L, and input the solution into a rectification tower with an absolute pres...

Embodiment 3

[0022] In this embodiment, the solvent is recycled through the following steps: add calcium hydroxide to the washing solution to obtain a neutralizing solution with pH=7, pass the neutralizing solution through a bag filter with a filtration accuracy of 2um, and collect the filtrate in a storage tank , the filtrate is sent to the dehydration system for dehydration by vacuum distillation, the distillation parameters are an absolute pressure of 4KPa and a temperature of 80°C. Then add 1% methanol additive to the solution, and send the solution into the crude distillation system, control the absolute pressure in the crude distillation tower to 1KPa, the temperature is 80°C, and the water content in the solution after crude distillation is <0.8%. Add anhydrous calcium chloride to the crude distillation solution to obtain a solution with a calcium chloride concentration of 0.17 mol / L, and input the solution into a rectification tower with an absolute pressure of 0.8KPa and a temperat...

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