Search

CN-122017127-A - Method for measuring residual acrylonitrile content in polyacrylonitrile polymer solution

CN122017127ACN 122017127 ACN122017127 ACN 122017127ACN-122017127-A

Abstract

The invention relates to a method for measuring the content of residual acrylonitrile in polyacrylonitrile polymer solution, which relates to the technical field of chemical analysis. The method comprises the steps of stirring and dissolving a polyacrylonitrile polymer liquid sample by using AN organic solvent, diluting by using water to obtain a sample solution, adding a salting-out agent into the sample solution, standing for a set time after stirring and dissolving to obtain a solution after adding the salting-out agent, adding a sodium sulfite solution into the solution after adding the salting-out agent, carrying out AN addition reaction on sodium sulfite and acrylonitrile AN under a heating condition, cooling after the set time of reaction to terminate the reaction, obtaining a reaction product mixture, carrying out solid-liquid separation on the reaction product mixture to obtain a filtrate, titrating the filtrate and a blank sample by adopting AN acid-base back titration method, and then calculating the residual acrylonitrile content in the polyacrylonitrile polymer liquid according to experimental data. The method has the advantages of high accuracy, good repeatability and convenient operation.

Inventors

  • WANG XIUXIU
  • LEI AIMIN
  • ZHOU GUOSHI
  • HOU MENGXUE
  • BI JIAQI
  • CUI YUHONG

Assignees

  • 山西钢科碳材料有限公司

Dates

Publication Date
20260512
Application Date
20260413

Claims (18)

  1. 1. A method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution, comprising the steps of: A step of preparing a sample solution, which is to stir and dissolve a polyacrylonitrile polymer solution sample with an organic solvent and dilute the solution with water to obtain a sample solution; Adding a salting-out agent, namely adding the salting-out agent into the sample solution, stirring and dissolving the sample solution, and standing for a set time to enrich acrylonitrile, and releasing the acrylonitrile from PAN chain wrapping to obtain a solution added with the salting-out agent; adding sodium sulfite solution into the solution added with the salting-out agent, carrying out addition reaction on sodium sulfite and acrylonitrile AN under the heating condition, and cooling after the reaction is carried out for a set time to terminate the reaction to obtain a reaction product mixture; and the acid-base back titration method comprises the steps of titrating the filtrate and the blank sample by adopting an acid-base back titration method, and then calculating the residual acrylonitrile content in the polyacrylonitrile polymer solution according to experimental data.
  2. 2. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 1, wherein in said step of preparing a sample solution: the organic solvent is one or more of dimethyl sulfoxide DMSO, N-dimethylformamide DMF and N-methylpyrrolidone NMP.
  3. 3. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 1, wherein, in said salting-out agent adding step: the salting-out agent is any one or more of sodium chloride solid, sodium chloride solution, ammonium sulfate solid, ammonium sulfate solution, potassium chloride solid and potassium chloride solution.
  4. 4. A method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 3, wherein in said salting-out agent adding step: If the salting-out agent is liquid, the concentration of the salting-out agent in the solution added with the salting-out agent is required to be 0.3mol/L to 0.7mol/L.
  5. 5. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 4, wherein, in said salting-out agent adding step: If the salting-out agent is a liquid, the concentration of the salting-out agent in the solution after adding the salting-out agent is required to be 0.5mol/L.
  6. 6. A method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 3, wherein in said salting-out agent adding step: If the salting-out agent is solid, 1.46 g-4.38 g of the salting-out agent is needed to be added into each 80mL of sample solution.
  7. 7. A method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 3, wherein in said salting-out agent adding step: If the salting-out agent is solid, 2.34g of salting-out agent is added per 80mL of sample solution.
  8. 8. A method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 3, wherein in said salting-out agent adding step: if the salting-out agent is liquid, dropwise adding and stirring are needed when the salting-out agent is added into the sample solution; If the salting-out agent is solid, the salting-out agent is needed to be added into the sample solution for multiple times, and after the salting-out agent added in the previous time is dissolved, the salting-out agent in the next time is added.
  9. 9. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 1, wherein in the step of adding a salting-out agent, the salting-out agent is added into the sample solution, and after the salting-out agent is stirred and dissolved, the sample solution is allowed to stand for 5 minutes to 15 minutes to enrich acrylonitrile and is released from PAN chain wrapping.
  10. 10. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 1, wherein in said addition reaction step: The temperature of the addition reaction is 45-55 ℃, and the time of the addition reaction is 5-15 min.
  11. 11. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 10, wherein in said addition reaction step, the temperature of said addition reaction is 50 ℃, and the time of said addition reaction is 10min.
  12. 12. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 1, wherein in the addition reaction step, the cooling means is an ice bath or a cold water bath.
  13. 13. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 1, wherein said acid-base back titration step comprises: step 1), transferring all filtrate obtained in the addition reaction step into a volumetric flask, and then adding water to set scale marks to obtain constant volume solution with the volume of V Total (S) ; Taking out the constant volume solution with the volume of V Moving from the constant volume solution with the volume of V Total (S) , transferring the constant volume solution into a titration container, adding excessive acid standard solution with known concentration into the titration container by adopting a back titration method, adding a pH indicator into the titration container, then titrating by using alkali standard solution with known concentration until the color of the solution is changed from light pink to green, stopping titration, and recording the volume of consumed alkali standard solution as V Sample ; Adding excessive acid standard solution with known concentration into the blank sample by adopting a back titration method, adding a pH indicator into the blank sample, then titrating by adopting alkali standard solution with known concentration, stopping titrating when the color of the solution is changed from light pink to green, and recording the volume V White color of the alkali standard solution consumed by the blank experiment; And 4) calculating the residual acrylonitrile content in the polyacrylonitrile polymer solution according to the mass m Sample 、V Total (S) 、V Moving 、V Sample 、V White color of the polyacrylonitrile polymer solution sample.
  14. 14. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 13, wherein V Moving /V Total (S) is 1:10 to 1:1.
  15. 15. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 13, wherein the pH indicator is a mixed solution comprising methyl red and bromocresol green, and the mass ratio of the methyl red to the bromocresol green is 1:1-3:1.
  16. 16. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 15, wherein the mass ratio of methyl red to bromocresol green is 2:1.
  17. 17. The method of determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 15, wherein said pH indicator further comprises an ethanol solvent.
  18. 18. The method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution according to claim 15, wherein in said step 4), the residual acrylonitrile content in the polyacrylonitrile polymer solution is calculated using the following formula: ; wherein V Sample is the volume of the consumed alkali standard solution in the step 2), and the unit is mL; V White color is the volume of the alkali standard solution consumed in step 3), in mL; C Alkali is the concentration of the alkali standard solution, and the unit is mol/L; m Sample is the mass of the polyacrylonitrile polymer solution sample in g in the step of preparing the sample solution; v Total (S) is the total volume of the constant volume solution, and the unit is mL; V Moving is the volume of solution removed from the constant volume solution of volume V Total (S) in mL; Wherein V Moving /V Total (S) is the removal proportion of the solution; 0.053 is the millimole mass of acrylonitrile in g/mmol.

Description

Method for measuring residual acrylonitrile content in polyacrylonitrile polymer solution Technical Field The invention relates to the technical field of chemical analysis, in particular to a method for measuring the content of residual acrylonitrile in polyacrylonitrile polymer solution. Background Polyacrylonitrile (PAN) carbon fiber is widely applied to various fields of aerospace and the like due to a series of excellent performances, and the preparation of the Polyacrylonitrile (PAN) carbon fiber comprises three processes of polymerization, spinning and carbonization. The polymerization process is a source for producing carbon fibers and is one of key steps for producing high-quality filaments. Therefore, the content of residual acrylonitrile in the polyacrylonitrile polymer liquid must be accurately measured, so that the on-site process debugging can be better guided, and the quality of the carbon fiber of the product is further improved. In the prior art, the content of residual acrylonitrile in polyacrylonitrile polymer liquid is almost determined by adopting a chemical titration method, such as CN 106370773, and the main principle of the method is that acrylonitrile and sodium sulfite react in aqueous solution to generate quantitative NaOH solution, alizarin yellow R-jet vanillyl phenolphthalein is used as an indicator, the residual acrylonitrile content is calculated according to the volume of consumed sulfuric acid standard solution by titration with sulfuric acid standard solution. The method is the method with the highest utilization rate at present due to simple operation, but has certain defects, and mainly comprises the following steps of directly dissolving a polymer liquid sample by DMSO (dimethyl sulfoxide), adding a certain amount of water for subsequent detection, and changing the local osmotic pressure of the solution at the moment of adding water, wherein PAN chain aggregation even has part of precipitation. Because of the winding action of PAN polymer chains, part of AN monomer is physically 'wrapped' and is difficult to fully react with sodium sulfite, so that the detection result is lower, and the part of AN is released for a long time, so that the on-site process debugging cannot be effectively guided in time. In addition, the indicator adopted by the method is alizarin yellow R-thymolphthalein, the color change range of the indicator is wider, the color of the solution changes from light blue to yellow-green before and after titration, and the color change is not obvious. And the PAN separated out by adding water in the high-viscosity polymer solution, impurities in the DMSO solution, side reaction products generated by addition reaction and the like have larger interference, so that the judgment of the end point color change by operators is aggravated, the titration error is large, and the experimental result is inaccurate. In addition, there is also related art (CN 115616144B) that adopts a full-automatic potentiometric titrator to measure the residual acrylonitrile content in the polyacrylonitrile polymer solution, adopts a potential mutation or a fixed endpoint pH value to determine the reaction endpoint, so that the AN content detection accuracy reaches 0.1%. However, according to the full-automatic potentiometric titrator adopted by the method, the titration container is AN open beaker, the tightness is poor, AN is easy to volatilize in the reaction process, the measurement result is inaccurate, AN also has residues in the environment, and the human health is affected. In addition, when the instrument is detected, an operator can operate the instrument after training for a certain time, so that the labor cost is high and the time is long. Therefore, there is a need to develop a novel method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution to improve the detection accuracy. Disclosure of Invention In view of the above, the present invention provides a method for determining the content of residual acrylonitrile in a polyacrylonitrile polymer solution, and the main purpose is to improve the accuracy of detection. In order to achieve the above purpose, the present invention mainly provides the following technical solutions: in one aspect, embodiments of the present invention provide a method for determining the residual acrylonitrile content in a polyacrylonitrile polymer solution, comprising the steps of: A step of preparing a sample solution, which is to stir and dissolve a polyacrylonitrile polymer solution sample with an organic solvent and dilute the solution with water to obtain a sample solution; Adding a salting-out agent, namely adding the salting-out agent into the sample solution, stirring and dissolving the sample solution, and standing for a set time to enrich acrylonitrile, and releasing the acrylonitrile from PAN chain wrapping to obtain a solution added with the salting-out agent; adding sodium sulfite solution into the