A rapid online detection method for pH value of meta-aramid resin

Abstract

The present invention relates to the technical field of chemical material analysis and detection, and specifically to a rapid online detection method for the pH value of a meta-aramid resin: determining the contents of -CH groups and -NH groups of a standard sample by a near-infrared detection device; constructing a PLS theoretical model between the contents of -CH groups and -NH groups and known actual amino content and viscosity; determining the actual pH value of the standard sample, detecting the standard sample by a near-infrared detection device, and obtaining the amino content and viscosity determination calculated values ​​of each standard sample by a PLS theoretical model, and constructing a prediction model using the amino content and viscosity determination calculated values ​​of the standard sample and the actual pH value of the standard sample; using a near-infrared detection device to detect a meta-aramid resin solution to be detected, and calculating the pH value of the meta-aramid resin solution to be detected by a PLS theoretical model and a prediction model. The detection method can reduce manual sampling and improve production efficiency.

Description

Technical Field

[0001] The invention relates to a rapid online detection method for pH value of a meta-aramid resin, belonging to the technical field of chemical material analysis and detection. Background Art

[0002] Meta-aramid fiber is a special organic fiber material with excellent flame retardancy, high temperature resistance, high strength and chemical stability. It is widely used in electrical insulation materials, flame retardant fabrics, safety protection, high temperature filtration, aerospace, optical cable reinforcement, honeycomb structure and rubber skeleton reinforcement materials and ropes, etc. It is an important basic material related to the national economy and people's livelihood. It is widely used in electrical insulation materials, flame retardant fabrics, safety protection, high temperature filtration, aerospace, optical cable reinforcement, honeycomb structure and rubber skeleton reinforcement materials and ropes, etc. It is an important basic material related to the national economy and people's livelihood.

[0003] The conventional method for producing meta-aramid resin is to use meta-phenylenediamine and isophthaloyl chloride to react. As the reaction progresses, hydrogen chloride is gradually generated in the reaction system, causing the system to be acidic. A neutralization reaction is required to prepare a weakly alkaline meta-aramid resin solution. In order to control the pH value of the meta-aramid resin, a large number of pH value tests are required. Because if the pH value of the meta-aramid resin solution is not appropriate, it will affect the spinning process of the meta-aramid fiber and the performance indicators of the meta-aramid fiber product.

[0004] The meta-aramid numerical preparation system is an organic system. There is no water in the meta-aramid resin solution, so the hydrogen ions in the hydrochloric acid molecules cannot be ionized. In addition, the meta-aramid resin will solidify and precipitate in the water system, making it impossible to achieve online pH testing through conventional methods, and it can only be tested through in vitro sampling.

[0005] At present, the pH value test method of meta-aramid resin requires diluting the sample in water to ionize the hydrogen ions in the water and then testing it with pH testing equipment. This method cannot achieve rapid online monitoring, which reduces production efficiency. In addition, the manual sampling and testing process is time-consuming and labor-intensive, information feedback is not timely, and resources are wasted, resulting in low production efficiency. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides a rapid online detection method for the pH value of a meta-aramid resin. By using online detection equipment, manual sampling is reduced, production efficiency is improved, loss is reduced, and the stability of the test result is improved.

[0007] The technical solution of the present invention to solve the above technical problems is as follows: a rapid online detection method for the pH value of meta-aramid resin, the detection method is:

[0008] S1. Take several meta-aramid resin solution standard samples with known amino content and viscosity values, and measure the -CH group and -NH group content of each of the standard samples by near infrared detection equipment; then construct a PLS theoretical model between the -CH group, -NH group content and the known actual amino content and viscosity by near infrared detection equipment;

[0009] S2. Using a pH detection device to measure the actual pH value of each of the standard samples, detecting the standard samples by a near-infrared detection device and obtaining the amino content and viscosity measurement calculation value of each of the standard samples by a PLS theoretical model, and using the amino content, viscosity measurement calculation value and actual pH value of the standard samples to construct a prediction model of amino content, viscosity and pH;

[0010] S3. Place the detection probe of the near-infrared detection equipment in the meta-aramid resin solution to be detected, obtain the amino content and viscosity measurement values ​​of the meta-aramid resin solution to be detected through the infrared detection equipment and the PLS theoretical model, and calculate the pH value of the meta-aramid resin solution to be detected by the prediction model described in step S2 using the amino content and viscosity measurement values.

[0011] Furthermore, the detection conditions of the near-infrared detection equipment are: online detection, air as the background, transmission measurement, and a wavelength detection range of 10000-3500cm -1 , scanning times are 32-64 times, resolution is 8cm -1 , the optical path is 5mm, and the scan is repeated 3-5 times for each detection, and the average value is taken as the measurement data.

[0012] Furthermore, the PLS theoretical model is applicable to an amino content range of 1-6.5% and a viscosity range of 5-90 Po at 25°C.

[0013] Furthermore, the temperature of the meta-aramid resin solution detected by the near-infrared detection equipment is -5-15°C, and the polymer solid content of the meta-aramid resin solution is 12-15%.

[0014] Furthermore, the prediction model in step S2 is: y=0.032AB+1020A 2 +9*10 -5 B 2 , where y is the pH value of the meta-aramid resin solution; A is the amino content of the meta-aramid resin solution obtained by the near-infrared detection equipment and the PLS theoretical model, and the unit is %; and B is the viscosity value of the meta-aramid resin solution obtained by the near-infrared detection equipment and the PLS theoretical model, and the unit is Po.

[0015] Furthermore, in step S1, the amino content of each of the meta-aramid numerical solution standard samples is uniformly distributed in the range of 1-6.5%, and the 25°C viscosity of each of the meta-aramid numerical solution standard samples is uniformly distributed in the range of 5-90 Po; and the number of the meta-aramid numerical solution standard samples is not less than 3.

[0016] Furthermore, in step S1, the known amino content of the standard sample of the meta-aramid resin solution is obtained by taking 5 g of the meta-aramid resin solution, adding DMAC to dissolve, and diluting to 200 mL, then taking 2 mL in a 50 mL volumetric flask, adding the prepared p-dimethylaminobenzaldehyde indicator to dilute to volume, and using an ultraviolet spectrophotometer for detection, and the test wavelength is 440 nm.

[0017] Furthermore, in step S1, the known viscosity value of the meta-aramid resin solution standard sample is obtained by using a rotor viscometer to detect the viscosity of the meta-aramid resin solution, and the operating temperature of the rotor viscometer equipment is 25°C.

[0018] Further, in step S2, the method of using the pH detection device to determine the actual pH value of each of the standard samples is as follows: taking a meta-aramid resin solution standard sample, adding water to dilute, wherein the weight ratio of the meta-aramid resin solution standard sample to water is 5:1;

[0019] The pH of the standard sample of the meta-aramid resin solution diluted with water was tested using a pH meter, and the test temperature of the pH meter was 25±0.5°C.

[0020] The beneficial effects of the present invention are:

[0021] The detection method of the present invention can realize the online rapid detection of the pH value of the meta-aramid resin solution during the preparation of the meta-aramid resin, realize the real-time monitoring of the pH value during the production process, ensure the timeliness of the pH value data detection, and be more conducive to controlling the reaction process during the production process. In addition, the detection method does not require manual sampling, and does not require sample processing of the meta-aramid resin solution to be detected, thereby reducing manual errors, improving the stability of the test results, reducing labor costs, and improving production efficiency.

[0022] The detection method of the present invention adopts online near-infrared detection to solve the problem that the pH cannot be detected in anhydrous environment due to the inability to ionize hydrogen ions. By constructing a theoretical model of -NH, -CH groups, amino groups, and viscosity in the reaction system, and simulating the online curve of viscosity, amino groups, and pH, the pH in the reaction system is accurately calculated for real-time monitoring. The error of the detection data of the pH value of the detection method of the present invention is no more than ±0.05 compared with the conventional method. DETAILED DESCRIPTION

[0023] The specific implementation of the present invention is described in detail below. The present invention can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used are only for describing specific embodiments and are not intended to limit the present invention.

[0025] A rapid online detection method for pH value of meta-aramid resin, the detection method comprising:

[0026] S1. Take several meta-aramid resin solution standard samples with known amino content and viscosity value (resin viscosity at 25°C), and measure the -CH group and -NH group content of each standard sample by near infrared detection equipment (the measurement temperature condition is -5~15°C); then construct a PLS theoretical model between the -CH group, -NH group content and the known actual amino content and viscosity by near infrared detection equipment;

[0027] S2. Using a pH detection device to measure the actual pH value of each of the standard samples, detecting the standard samples by a near-infrared detection device and obtaining the amino content and viscosity measurement calculation value of each of the standard samples by a PLS theoretical model, and using the amino content, viscosity measurement calculation value and actual pH value of the standard samples to construct a prediction model of amino content, viscosity and pH;

[0028] The prediction model in step S2 is: y=0.032AB+1020A 2 +9*10 -5 B 2 , where y is the pH value of the meta-aramid resin solution; A is the amino content of the meta-aramid resin solution obtained by the near-infrared detection equipment and the PLS theoretical model, and the unit is %; and B is the viscosity value of the meta-aramid resin solution obtained by the near-infrared detection equipment and the PLS theoretical model, and the unit is Po.

[0029] S3. Place the detection probe of the near-infrared detection equipment in the meta-aramid resin solution to be detected, obtain the amino content and viscosity measurement values ​​of the meta-aramid resin solution to be detected through the infrared detection equipment and the PLS theoretical model, and calculate the pH value of the meta-aramid resin solution to be detected by the prediction model described in step S2 using the amino content and viscosity measurement values.

[0030] Specifically, the detection conditions of the near-infrared detection equipment are: online detection, air as the background, transmission measurement, and a wavelength detection range of 10000-3500cm-1 , scanning times are 32-64 times, resolution is 8cm -1 , the optical path is 5mm, and the scan is repeated 3-5 times for each detection, and the average value is taken as the measurement data.

[0031] Specifically, the PLS theoretical model is applicable to an amino content range of 1-6.5% and a viscosity range of 5-90 Po at 25°C.

[0032] Specifically, the temperature of the meta-aramid resin solution detected by the near-infrared detection equipment is -5-15°C, and the polymer solid content of the meta-aramid resin solution is 12-15%.

[0033] Specifically, in step S1, the amino content of each of the meta-aramid numerical solution standard samples is uniformly distributed in the range of 1-6.5%, and the 25°C viscosity of each of the meta-aramid numerical solution standard samples is uniformly distributed in the range of 5-90 Po; the number of the meta-aramid numerical solution standard samples is not less than 3.

[0034] Specifically, in step S1, the known amino content of the standard sample of the meta-aramid resin solution is obtained by taking 5 g of the meta-aramid resin solution, adding DMAC to dissolve, and diluting to 200 mL, then taking 2 mL in a 50 mL volumetric flask, adding the prepared p-dimethylaminobenzaldehyde indicator to dilute to volume, and using an ultraviolet spectrophotometer for detection, and the test wavelength is 440 nm.

[0035] Specifically, in step S1, the known viscosity value of the meta-aramid resin solution standard sample is obtained by using a rotor viscometer to detect the viscosity of the meta-aramid resin solution, and the operating temperature of the rotor viscometer equipment is 25°C.

[0036] Specifically, in step S2, the method of using the pH detection device to determine the actual pH value of each of the standard samples is as follows: taking a meta-aramid resin solution standard sample, adding water to dilute it, wherein the weight ratio of the meta-aramid resin solution standard sample to water is 5:1;

[0037] The pH of the standard sample of the meta-aramid resin solution diluted with water was tested using a pH meter, and the test temperature of the pH meter was 25±0.5°C.

[0038] Examples 1-12

[0039] In the process of preparing the meta-aramid resin solution, the pH value of the meta-aramid resin solution is measured using the analytical method of the present invention. The near-infrared detection equipment used in the embodiment of the present invention is a DA200 online near-infrared analyzer.

[0040] In addition, the conventional method is used for simultaneous manual sampling, and the specific method is: take the meta-aramid resin solution to be tested, add water for dilution, wherein the weight ratio of the meta-aramid resin solution standard sample to water is 5:1; use a pH meter to test the pH of the meta-aramid resin solution standard sample after dilution with water, and the test temperature of the pH meter is 25±0.5°C. The specific test results are shown in Table 1 below.

[0041] Table 1 Analysis and test results

[0042]

[0043] From the above table data, it can be seen that in the detection method of the present invention, a PLS theoretical model of -NH, -CH group content, amino content and viscosity in the reaction system is constructed, and the pH in the reaction system is accurately calculated by simulating the online curve of viscosity, amino content and pH, so as to achieve real-time monitoring of pH in the preparation process of meta-aramid resin and control the reaction process. It reduces manual sampling, improves production efficiency, reduces losses, and improves the stability of test results. The error of the detection data of pH value of the detection method of the present invention is no more than ±0.02 compared with the conventional method.

[0044] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are exhaustively listed. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0045] For those skilled in the art, several modifications and improvements may be made without departing from the concept of the present invention, all of which belong to the protection scope of the present invention. The protection scope of the present invention shall be based on the attached claims.

Claims

1. A rapid online detection method for pH value of meta-aramid resin, characterized in that: The detection method is: S1. Take several meta-aramid resin solution standard samples with known amino content and viscosity values, and measure the -CH group and -NH group content of each of the standard samples by near infrared detection equipment; then construct a PLS theoretical model between the -CH group, -NH group content and the known actual amino content and viscosity by near infrared detection equipment; S2. Using a pH detection device to measure the actual pH value of each of the standard samples, detecting the standard samples by a near-infrared detection device and obtaining the amino content and viscosity measurement calculation value of each of the standard samples by a PLS theoretical model, and using the amino content, viscosity measurement calculation value and actual pH value of the standard samples to construct a prediction model of amino content, viscosity and pH; S3. Place the detection probe of the near-infrared detection equipment at the meta-aramid resin solution to be detected, obtain the amino content and viscosity measurement values ​​of the meta-aramid resin solution to be detected through the infrared detection equipment and the PLS theoretical model, and calculate the pH value of the meta-aramid resin solution to be detected by the prediction model described in step S2 using the amino content and viscosity measurement values.

2. According to claim 1, a rapid online detection method for pH value of meta-aramid resin is characterized in that: The detection conditions of the near infrared detection equipment are: online detection, air as background, transmission sampling method, and wavelength detection range of 10000-3500cm -1 , scanning times are 32-64 times, resolution is 8cm -1 , the optical path is 5mm, and the scan is repeated 3-5 times for each detection, and the average value is taken as the measurement data.

3. According to claim 1, a rapid online detection method for pH value of meta-aramid resin is characterized in that: The PLS theoretical model is applicable to an amino content range of 1-6.5% and a viscosity range of 5-90 Po at 25°C.

4. The method for rapid online detection of pH value of meta-aramid resin according to claim 1, characterized in that: The temperature of the meta-aramid resin solution detected by the near-infrared detection equipment is -5-15° C., and the polymer solid content of the meta-aramid resin solution is 12-15%.

5. The method for rapid online detection of pH value of meta-aramid resin according to claim 1, characterized in that: The prediction model in step S2 is: y=0.032AB+1020A 2 +9*10 -5 B 2 , where y is the pH value of the meta-aramid resin solution; A is the amino content of the meta-aramid resin solution obtained by the near-infrared detection equipment and the PLS theoretical model, and the unit is %; and B is the viscosity value of the meta-aramid resin solution obtained by the near-infrared detection equipment and the PLS theoretical model, and the unit is Po.

6. The method for rapid online detection of pH value of meta-aramid resin according to claim 1, characterized in that: In step S1, the amino content of each of the meta-aramid numerical solution standard samples is uniformly distributed in the range of 1-6.5%, and the 25°C viscosity of each of the meta-aramid numerical solution standard samples is uniformly distributed in the range of 5-90 Po; the number of the meta-aramid numerical solution standard samples is not less than 3.

7. The method for rapid online detection of pH value of meta-aramid resin according to claim 1, characterized in that: In step S1, the known amino content of the meta-aramid resin solution standard sample is obtained by taking 5 g of the meta-aramid resin solution, adding DMAC to dissolve, and diluting to 200 mL, then taking 2 mL in a 50 mL volumetric flask, adding the prepared p-dimethylaminobenzaldehyde indicator to dilute to volume, and using an ultraviolet spectrophotometer for detection, and the test wavelength is 440 nm.

8. The method for rapid online detection of pH value of meta-aramid resin according to claim 1, characterized in that: In step S1, the known viscosity value of the meta-aramid resin solution standard sample is obtained by using a rotor viscometer to detect the viscosity of the meta-aramid resin solution, and the operating temperature of the rotor viscometer equipment is 25°C.

9. The method for rapid online detection of pH value of meta-aramid resin according to claim 1, characterized in that: In step S2, the method of using a pH detection device to determine the actual pH value of each of the standard samples is as follows: taking a meta-aramid resin solution standard sample, adding water to dilute it, wherein the weight ratio of the meta-aramid resin solution standard sample to water is 5:1; The pH of the meta-aramid resin solution standard sample diluted with water was tested using a pH meter, and the test temperature of the pH meter was 25±0.5°C.

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