Method for on-line analysis of the concentration of a chlorobutadiene polymer aqueous phase liquid component

Abstract

The application belongs to the technical field of synthetic chloroprene rubber, and aims to solve the problems of high labor intensity, long time, prolonged water phase preparation cycle and reduced production efficiency in the component concentration analysis method of the water phase preparation of synthetic chloroprene rubber, and provides a kind of on-line analysis method for component concentration of chlorobutadiene polymerization water phase liquid. The factors affecting the conductivity of electrolyte solution include ion concentration, temperature and valence of ions. The on-line conductivity analysis method is used to determine the concentration of naphthylamine sulfonic acid formaldehyde polycondensate sodium salt, potassium hydroxide and sodium sulfite in the water phase liquid, and the relationship between the conductivity and the concentration of the water phase components is established: the relationship between the conductivity and the concentration of PW, potassium hydroxide and sodium sulfite, respectively. Through on-line measurement of the conductivity of the water phase liquid, the on-line monitoring of the component concentration of the polymerization water phase liquid is realized. The labor intensity is reduced, the work efficiency is improved, the analysis time of single water phase preparation is shortened from 2 hours to 6 minutes, and the influence of water phase sampling analysis on production is solved.

Description

Technical Field

[0001] This invention belongs to the field of synthetic chloroprene rubber technology, specifically relating to an online method for analyzing the concentration of components in an aqueous phase of chloroprene polymerization. Background Technology

[0002] The production of chloroprene rubber employs emulsion polymerization technology, which involves emulsifying and polymerizing a prepared aqueous and oil phase. Current methods for preparing the aqueous phase include first adding demineralized water, then adding a measured amount of sodium naphthylamine sulfonate formaldehyde condensate (PW), circulating the solution until it reaches 35°C, then adding potassium hydroxide. After stirring for 20 minutes, a sample is manually taken and the PW concentration is analyzed using a spectrophotometer, while the potassium hydroxide concentration is analyzed using hydrochloric acid titration. After passing these tests, sodium sulfite is added 30 minutes before emulsification, and the mixture is stirred for 15 minutes. The sodium sulfite concentration is then manually analyzed again using hydrochloric acid titration. This method of component concentration analysis during aqueous phase preparation is labor-intensive and time-consuming, extending the preparation cycle and reducing production efficiency. Summary of the Invention

[0003] To address the problems of high labor intensity, long preparation time, and reduced production efficiency in the aqueous phase preparation of chloroprene rubber during synthesis, this invention provides an online method for analyzing the concentration of components in the aqueous phase of chloroprene polymerization, enabling online monitoring.

[0004] This invention is achieved using the following technical solution: an online method for analyzing the concentration of components in an aqueous phase of chloroprene polymerization, which uses online conductivity analysis to determine the concentrations of PW, potassium hydroxide, and sodium sulfite in the aqueous phase. The specific steps are as follows:

[0005] (1) Establishing the relationship between aqueous component concentration and conductivity: According to the production process control, prepare solutions of PW, potassium hydroxide, and sodium sulfite with different concentration gradients, measure the conductivity, plot the working curve with conductivity on the x-axis and the concentration of each component on the y-axis, and establish the relationship between aqueous component concentration and conductivity, as follows:

[0006] A. Establish the relationship between PW concentration and conductivity: Weigh seven PW samples with a mass gradient distribution from 2.75g to 4.25g, and dilute them to 500ml in a volumetric flask. Calculate the mass fraction of PW, measure the conductivity of the solution, and then plot the PW standard curve to obtain the corresponding relationship.

[0007] B. Establish the relationship between potassium hydroxide concentration and conductivity: Weigh 16.00g of PW and make up to 2000ml in a volumetric flask. Measure 250mL of each flask into 7 beakers and add KOH in a gradient distribution from 0.6228g to 0.8185g. Standardize the KOH concentration using potassium hydrogen phthalate and measure its conductivity. Plot a standard curve for potassium hydroxide to obtain the corresponding relationship.

[0008] C. Establishing the relationship between sodium sulfite concentration and conductivity: Weigh 16.00 g of PW and place it in a 2000 ml beaker. Add 1000 ml of water to dissolve it, then add 4.4200 g of KOH and stir to dissolve. Make up the volume to a 2000 ml volumetric flask. Take 250 mL of the solution and place it in seven beakers. Add sodium sulfite in a gradient distribution from 1.5330 g to 1.7130 g and measure its conductivity. Then plot the sodium sulfite standard curve to obtain the corresponding relationship.

[0009] (2) Prepare a solution of PW, potassium hydroxide and sodium sulfite according to the method in step (1), and measure the conductivity of the solution in the temperature range of 25℃ to 50℃;

[0010] (3) Selection and online installation measurement: Select online measurement electrodes and transmitters and perform measurements;

[0011] (4) Significance test of online measurement and manual chemical analysis results: P=0.95, F=2.97, t=2.12 when degrees of freedom are 18. There was no significant difference between chemical analysis and online conductivity analysis in measuring the concentrations of PW, potassium hydroxide and sodium sulfite in aqueous solution.

[0012] The conductivity was measured in the laboratory using a calibrated DDSJ-307 conductivity meter, and in the industrial production field, it was measured online using a Honeywell 04973 conductivity electrode.

[0013] Factors affecting the conductivity of electrolyte solutions include ion concentration, temperature, and ion valence. In the aqueous polymerization solution, the ion valences of PW, potassium hydroxide, and sodium sulfite are fixed. The measurement temperature range is relatively fixed, and the conductivity meter has an automatic temperature compensation function. The effect of temperature on the conductivity of the aqueous solution is observed simultaneously. The conductivity of PW, potassium hydroxide, and sodium sulfite in the aqueous solution within the process control concentration range depends on their ion concentrations. The relationship between the concentration of aqueous solution components and conductivity is established. Online monitoring of the concentration of components in the aqueous polymerization solution is achieved through online measurement of the aqueous solution conductivity.

[0014] This invention uses conductivity analysis to determine the concentrations of PW, potassium hydroxide, and sodium sulfite in an aqueous solution. Based on the relationship between the concentrations of PW, potassium hydroxide, and sodium sulfite solutions and their conductivity values, the concentrations of the solution components are calculated by measuring the solution's conductivity. In this invention, the relationship between the concentrations of PW, potassium hydroxide, and sodium sulfite solutions and their conductivity values ​​is obtained in a laboratory setting. In the laboratory setting, conductivity is measured using a calibrated DDSJ-307 conductivity meter, potassium hydroxide concentration is measured using potassium hydrogen phthalate (a standard reagent), and the concentrations of PW and sodium sulfite are directly prepared and calculated.

[0015] The effect of temperature on conductivity measurements: Temperature affects the measured conductivity value. Conductivity meters have an automatic temperature compensation function, which automatically corrects the conductivity measurements taken at different temperatures to the value measured at 25℃. Prepare a solution of PW, potassium hydroxide, and sodium sulfite according to the above solution preparation method. Observe the conductivity values ​​of the solution by changing the solution temperature.

[0016] The beneficial effects of this invention are as follows: This invention enables online measurement of the concentrations of PW, potassium hydroxide, and sodium sulfite components in the aqueous phase during the polymerization of chloroprene rubber, reducing labor intensity, improving work efficiency, and shortening the time for a single aqueous phase preparation and analysis from 2 hours to 6 minutes, thus solving the impact of aqueous phase sampling and analysis on production. Attached Figure Description

[0017] Figure 1 The conductivity curve of PW is shown in the figure.

[0018] Figure 2 A working curve showing the relationship between the mass fraction of potassium hydroxide and the increase in conductivity;

[0019] Figure 3 A working curve showing the relationship between the mass fraction of sodium sulfite and the increase in conductivity;

[0020] Figure 4 The data are for online measurement of the conductivity of aqueous components using a Honeywell 04973 conductivity electrode; the horizontal axis represents the time of addition of materials such as PW, potassium hydroxide, and sodium sulfite, and the vertical axis represents the corresponding online conductivity value. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains, and all materials publicly cited herein and cited by them are incorporated herein by reference.

[0023] Equivalent technologies of the specific embodiments described herein that are readily apparent to those skilled in the art through routine experimentation are included in this application.

[0024] Unless otherwise specified, the experimental methods used in the following examples are conventional methods. Unless otherwise specified, the instruments and equipment used in the following examples are all standard laboratory instruments and equipment; unless otherwise specified, the experimental materials used in the following examples were all purchased from regular biochemical reagent stores.

[0025] Instruments and reagents: DDSJ-307 conductivity meter, UD-2500 UV-Vis spectrophotometer, potassium hydrogen phthalate, sodium sulfite (analytical grade), HCl standard solution.

[0026] Example 1: An online method for analyzing the component concentration of chloroprene polymerization aqueous solution, the specific method is as follows:

[0027] 1. Establish the relationship between aqueous component concentration and conductivity: Based on the production process control, prepare solutions of PW, potassium hydroxide, and sodium sulfite with different concentrations, measure the conductivity, plot the working curve with conductivity on the x-axis and the concentration of each component on the y-axis, and establish the relationship between aqueous component concentration and conductivity.

[0028] A. Relationship between PW concentration and conductivity

[0029] (1) Solution preparation: Weigh seven PW solutions with a mass gradient distribution of 2.75g to 4.25g, and dilute them to 500ml in volumetric flasks. Calculate the solution volume from 1.1 to 1.7, measure their conductivity, and calculate the mass fraction of PW. The corresponding results of the mass fraction of PW solution and conductivity values ​​are shown in Table 1.

[0030] Table 1. Mass fraction and conductivity of PW solution

[0031]

[0032] (2) Standard curve plotting: Plot a graph with conductivity on the x-axis and PW mass fraction on the y-axis. The working curve of PW mass fraction versus conductivity value is shown below. Figure 1 As shown, the PW mass fraction and conductivity value exhibit a linear relationship: .

[0033] B. Relationship between potassium hydroxide concentration and conductivity:

[0034] (1) Solution preparation: Weigh 16.0000g of PW and dilute to 2000ml in a volumetric flask. The conductivity of solution 2.0 is measured to be 2.10. Measure 300g of solution 2.0 (accurate to 0.0001g) and place them in 7 beakers. Add 0.6228g to 0.8185g of KOH in a gradient distribution from solution 2.1 to 2.7. Measure and calculate the increase in conductivity. Use potassium hydrogen phthalate as a primary standard to standardize the concentration of potassium hydroxide. The results are shown in Table 2.

[0035] Table 2. KOH mass fraction and increase in conductivity

[0036]

[0037] (2) Standard curve plotting: Plot a graph with the increase in conductivity on the x-axis and the mass fraction of potassium hydroxide on the y-axis. The working curve of potassium hydroxide mass fraction versus conductivity is shown below. Figure 2 As shown, the increase in conductivity is linearly related to the mass fraction of potassium hydroxide. .

[0038] C. Relationship between sodium sulfite concentration and conductivity

[0039] (1) Solution preparation: Weigh 14.0020g PW and 5.2820g KOH and make up to 2000ml in a volumetric flask, which is recorded as solution 3.0. Its conductivity is measured to be 14.52. Measure 100g of solution 3.0 (accurate to 0.0001g) and place them in 8 beakers, which are then labeled as solutions 3.1 to 3.8. Add 0.4233g to 0.5840g of Na2SO3 in a gradient distribution, and measure and calculate the increase in conductivity. The results are shown in Table 3.

[0040] Table 3. Increase in conductivity based on Na2SO3 mass fraction

[0041]

[0042] (2) Standard curve plotting: Plot the increase in conductivity on the x-axis and the sodium sulfite mass fraction on the y-axis. The working curve is shown in Figure 3. The sodium sulfite mass fraction and the increase in conductivity show a linear relationship: .

[0043] D. Effect of temperature on conductivity measurements: The process control temperature range of PW, potassium hydroxide, and sodium sulfite solutions in the aqueous phase was relatively fixed, and the conductivity meter had an automatic temperature compensation function. The effect of temperature on the conductivity of the aqueous phase solution was observed within the range of 25℃ to 50℃. The results are shown in Table 4.

[0044] Table 4 Effect of Temperature on Conductivity

[0045]

[0046] The results show that within the temperature range of 25℃ to 50℃, temperature compensation can effectively eliminate the influence of temperature changes on conductivity.

[0047] 2. Selection and online installation measurement: Considering the measurement of strong alkaline solutions such as potassium hydroxide, the 40 flange at the bottom of the on-site aqueous phase tank and pipelines, and the addition of large materials during the aqueous phase preparation process, and in conjunction with relevant manufacturers and the operating conditions of our plant's instruments, Honeywell 04973 conductivity electrodes were installed at the bottom of the polymerization aqueous phase tank to measure the conductivity of the aqueous phase components online; an APT2000 transmitter was used to transmit the data to the database.

[0048] Retrieving online measurement data, such as Figure 4 As shown in the figure, the horizontal axis represents the time of addition of PW, potassium hydroxide, sodium sulfite, and other materials. The vertical axis represents the corresponding online conductivity value. Based on the relationship between aqueous phase component concentration and conductivity established in Example 1, the corresponding component concentration was calculated based on the online measured conductivity.

[0049] 3. Comparison between online conductivity measurement method and on-site sampling chemical analysis method for aqueous component concentration

[0050] A. Comparison of measurement results

[0051] The F-test was used to analyze the variance S of the two sets of data. 2 To determine whether there is a significant difference in the precision of the two sets of data, a t-test is used to determine whether there is a significant difference between the average values ​​of the two sets of measurement results.

[0052] According to the formula: Calculate the F-value; according to the formula: Calculate the t-value (x is the average value, n is the number of measurements, and s is the pooled standard deviation). The calculation results are shown in Table 5.

[0053] Table 5. Significance Test F-values ​​and t-values

[0054]

[0055] Conclusion: After 10 measurements, referring to the F-value table, the result is (P=0.90) F 表 =2.97. The F-values ​​calculated in Table 5 are all less than 2.97, indicating that there is no significant difference in the precision of the two analytical methods in measuring the concentrations of PW, alkali, and sodium sulfite. (Check...) The value table shows that when P=0.95 and the total degrees of freedom are 18, The t-values ​​calculated in Table 5 are all less than 2.12. Therefore, with a confidence level of 0.95, it is considered that there is no significant difference between the means of the two analytical methods when analyzing the concentrations of alkali, PW, and sodium sulfite.

[0056] B. Method Comparison

[0057] The measurement methods and analysis times of online conductivity measurement and on-site sampling chemical analysis of aqueous phase component concentrations were compared. The comparison results are shown in Table 6.

[0058] Table 6

[0059]

[0060] Conclusion: The original chemical analysis method took approximately 2 hours to analyze the concentration of aqueous components, with an average of 10 aqueous phase preparations per day, resulting in a total analysis time of 20 hours per day. The current linear conductivity measurement method eliminates the need for manual sampling and analysis, taking approximately 1 hour per day.

[0061] This invention enables online measurement of the concentrations of PW, potassium hydroxide, and sodium sulfite components in the aqueous phase of chloroprene rubber polymerization, reducing labor intensity and improving work efficiency. The time for a single aqueous phase preparation and analysis is shortened from 2 hours to 6 minutes. It also addresses the impact of aqueous phase sampling and analysis on production.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for online analysis of component concentrations in an aqueous phase of chloroprene polymerization, characterized in that: The concentrations of PW, potassium hydroxide, and sodium sulfite in the aqueous solution were determined using online conductivity analysis. The specific steps are as follows: (1) Establishing the relationship between aqueous component concentration and conductivity: According to the production process control, prepare solutions of PW, potassium hydroxide, and sodium sulfite with different concentration gradients, measure the conductivity, plot the working curve with conductivity on the x-axis and the concentration of each component on the y-axis, and establish the relationship between aqueous component concentration and conductivity, as follows: A. Establishing the relationship between PW concentration and conductivity: Weigh seven PW fractions (2.75g to 4.25g) in a gradient distribution, and dilute to 500ml in a volumetric flask. Calculate the PW mass fraction, measure the conductivity of the solution, and then plot a PW standard curve to obtain the corresponding relationship. The PW mass fraction and conductivity value exhibit a linear relationship. ; B. Establishing the relationship between potassium hydroxide concentration and conductivity: Weigh 16.00 g of PW and dilute to 2000 ml in a volumetric flask. Measure 250 mL of each flask into seven beakers. Add KOH in a gradient distribution from 0.6228 g to 0.8185 g. Standardize the KOH concentration using potassium hydrogen phthalate and measure its conductivity. Plot a potassium hydroxide standard curve. The corresponding relationship is obtained: the mass fraction of potassium hydroxide and the increase in conductivity exhibit a linear relationship. ; C. Establishing the relationship between sodium sulfite concentration and conductivity: Weigh 16.00 g of PW and place it in a 2000 ml beaker, add 1000 ml of water to dissolve it, then add 4.4200 g of KOH and stir to dissolve. Make up the volume to a 2000 ml volumetric flask. Take 250 mL of the solution and place it in seven beakers. Add sodium sulfite in a gradient distribution from 1.5330 g to 1.7130 g and measure its conductivity. Then plot the sodium sulfite standard curve. The corresponding relationship is obtained: the mass fraction of sodium sulfite and the increase in conductivity have a linear relationship. ; (2) Prepare a solution of PW, potassium hydroxide and sodium sulfite according to the method in step (1), and measure the conductivity of the solution in the temperature range of 25℃ to 50℃; (3) Selection of online installation measurement: Select online measurement electrodes and transmitters for measurement; (4) Significance test of results between online conductivity measurement method and on-site sampling chemical analysis method: The F test was used to measure the variance S of the two sets of data. 2 To determine whether there is a significant difference in the precision of the two sets of data, a t-test is used to determine whether there is a significant difference between the average values ​​of the two sets of measurement results. According to the formula: Calculate the F-value; according to the formula: Calculate the t-value, where x is the average value, n is the number of measurements, and s is the pooled standard deviation. The calculation results show that there is no significant difference between the mean values ​​of the two analytical methods when analyzing the concentrations of alkali, PW, and sodium sulfite.

2. The method for online analysis of component concentration in aqueous phase of chloroprene polymerization according to claim 1, characterized in that: The conductivity was measured in the laboratory using a calibrated DDSJ-307 conductivity meter, and in the industrial production field, it was measured online using a Honeywell 04973 conductivity electrode.

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