Method for on-line detection of olefin monomer content in circulating solvent in abs production process

Abstract

The application discloses an online detection method for olefin monomer content in ABS production process circulating solvent, belongs to the field of organic chemical synthesis and online analysis and mainly relates to the field of ABS production process monitoring. The method comprises the following steps: constructing an online detection system for the olefin monomer content at a circulating solvent process detection position, detecting original characteristic spectrum through a Raman spectrum characteristic method and obtaining spectrum; performing pretreatment operation on the obtained original spectrum before feature extraction, determining suitable features in combination with the difference of intensity change at each position of the spectrum signal after pretreatment, extracting features in combination with the spectrum signal of different olefin monomer contents, establishing a quantitative model for the corresponding feature peak intensity and content value, and realizing online detection of the olefin monomer sample content through the model. The application has the advantages of small demand for training samples for model establishment through the Raman spectrum, short component analysis time, accurate prediction result and suitability for online quantitative analysis and detection of the olefin monomer content.

Description

Technical Field

[0001] This invention relates to the field of organic chemical synthesis and online analysis, mainly to the field of ABS production process monitoring, and specifically to an online detection method for the content of olefin monomers in the circulating solvent of ABS production process. Background Technology

[0002] ABS resin is a copolymer of acrylonitrile (AN), butadiene (BD), and styrene (SM). Its properties depend on the ratio of the three components, their chemical structures, and physical forms. Acrylonitrile possesses heat resistance, chemical resistance, rigidity, and tensile strength; butadiene exhibits high impact resistance; and styrene contributes to processing fluidity and gloss. The combination of these three components, with their complementary advantages, gives ABS resin excellent overall performance, making it widely used in electronics, electrical appliances, instruments, automobiles, building materials, and daily consumer goods.

[0003] Currently, the mainstream production processes for ABS resin can be divided into emulsion grafting-bulk SAN (a copolymer of SM and AN) blending method and continuous bulk method.

[0004] The emulsion grafting-bulk SAN blending process is shown in the attached figure. Figure 1 As shown, the process mainly consists of four units: butadiene latex preparation, latex grafting and drying, bulk SAN polymerization, and blending and granulation. First, polybutadiene latex is obtained through emulsion polymerization. Then, styrene and acrylonitrile monomers are added for emulsion grafting to obtain grafted latex. The grafted latex undergoes coagulation, dehydration, and drying to obtain ABS grafted powder. Simultaneously, styrene and acrylonitrile monomers undergo bulk polymerization to obtain bulk SAN resin. Finally, the ABS grafted powder and bulk SAN resin are blended, extruded, and granulated to obtain the ABS resin product. While the above emulsion grafting-blending process has many advantages, it also has significant drawbacks. Due to inherent limitations, the purity of the ABS product is relatively poor, with a high residual monomer content, and the production process generates large amounts of wastewater and toxic exhaust gases. These problems are becoming increasingly prominent, especially given the increasingly stringent national environmental protection requirements.

[0005] The continuous bulk method process is shown in the attached figure. Figure 2As shown, the main processes include sol-gel, polymerization, devolatilization, and granulation. First, butadiene rubber is dissolved in monomers (SM, AN) and a small amount of solvent under stirring conditions to form a glue solution. The glue solution is heated to a certain temperature through a preheater and then transported to a polymerization reactor, where an initiator and molecular weight regulator are added for graft polymerization. Next, the reactants are transported to a devolatilization unit to remove the solvent and unreacted monomers. Finally, the devolatilized polymer is extruded and granulated to obtain the ABS resin product. Compared to the emulsion method, continuous bulk ABS technology has significant advantages such as shorter process, lower energy consumption, lower investment, and environmental friendliness. Its products are characterized by a white base color, resistance to yellowing, and low residual monomers, meeting the stringent material performance requirements of fields such as automotive interiors, high-end home appliances, and electronic appliances.

[0006] Whether it is the emulsion grafting-bulk SAN blending process or the continuous bulk process, the solvent and unreacted monomers separated by the devolatilization unit after the polymerization reaction (collectively referred to as "circulating solvent") will be returned to the feed port of the polymerization reactor. At the same time, fresh styrene and acrylonitrile will be added and reintroduced into the reaction system as a homogeneous mixture (for the continuous bulk process, butadiene rubber is dissolved in the above mixture under stirring conditions to form a glue).

[0007] To ensure the olefin monomer ratio in the reaction feed meets design requirements, strict monitoring and control of the feed content are necessary. Since fresh styrene and acrylonitrile are nearly pure components, while the content of each component in the circulating solvent varies considerably, real-time monitoring of the circulating solvent flow rate and the content of each component is required to strictly control the component distribution in the feed.

[0008] For online detection of the content of each component in circulating solvents, gas chromatography is the commonly used method. However, online chromatographs suffer from severe response lag (≥10 minutes for a single flow path), leading to delays in process adjustments; olefin monomers are prone to polymerization and clogging of the chromatographic sampling lines; the pretreatment system is complex and has a high failure rate; furthermore, it requires regular replacement of consumables and frequent calibration with standard gases, resulting in a large amount of daily on-site maintenance. Therefore, it is difficult to meet the above detection requirements. In contrast, online Raman spectroscopy offers fast detection speed (≤1 minute for a single flow path), high detection accuracy, requires no sample pretreatment, and is nearly maintenance-free on-site, making it particularly suitable for the online detection of the aforementioned olefin monomer mixtures. In actual production processes, circulating solvents include toluene, ethylbenzene, and other solvents in addition to olefin monomers; and the detection parameter is the content (mass percentage, wt%) of each olefin component. Summary of the Invention

[0009] The purpose of this invention is to address the shortcomings of existing technologies by proposing an online detection method for the olefin monomer content in the circulating solvent of the ABS production process.

[0010] The objective of this invention is achieved through the following technical solution: an online detection method for the olefin monomer content in the circulating solvent of an ABS production process, comprising the following steps: (1) Construct an online detection system for olefin monomer content at the detection point of the circulating solvent process, including a laser, spectrometer, signal communication equipment, Raman probe, optical cable and other electrical equipment; (2) Based on the online detection system, the original optical signal of the olefin monomer mixture that enters the circulation loop after the main polymerization reaction is collected, and the signal is converted into a digital electrical signal to obtain the original spectral signal of different monomer mixtures; (3) Perform preprocessing operations on the original spectral signal; (4) Combine the Raman spectra of the pure component standard substances in the circulating solvent to find new olefin features and perform spectral signal feature analysis. By analyzing the different signal intensities of different spectral bands of the pretreated olefin mixture, the correlation between the signal intensity of each spectral band and the olefin content is analyzed. The spectral band with a large correlation between signal intensity and content is selected and the consistency of the spectral feature positions corresponding to the selected olefin features is verified. A mathematical feature model of spectral signal intensity and olefin monomer content is constructed. (5) Measure the spectrum of the olefin monomer mixture sample to be tested, perform preprocessing, input the preprocessed spectrum of the olefin monomer mixture sample to be tested into the feature model constructed in step (4), and output the content of each olefin monomer in the sample to be tested.

[0011] Further, step (1) includes: using an excitation wavelength of 785nm and a detection range of 400-2200cm. -1 A laser was used to perform Raman spectroscopy analysis on an olefin mixture.

[0012] Furthermore, the olefin monomer mixture is a mixture of reaction raw materials in the ABS production unit, and the olefin content varies in different olefin mixtures.

[0013] Furthermore, the preprocessing of the spectral signal includes noise suppression, spectral signal smoothing, signal baseline correction, and spectral signal enhancement processing based on the characteristics of various monomers in the monomer mixture.

[0014] Furthermore, the spectral signal feature analysis specifically involves combining the method of selecting the mechanistic characteristic peaks of the standard Raman spectrum of the pure component with the method of performing correlation analysis on the actual acquired spectrum to obtain features that conform to the theoretical characteristic spectral bands of each component and the correlation between the actual measured spectrum and the content.

[0015] Furthermore, the novel olefin features include: a wavenumber position including, but not limited to, 400-500 cm⁻¹. -1 Spectral range, 600-650 cm -1Spectral range, 750-800 cm -1 Spectral bands, and 1001 cm -1 1034 cm -1 1183 cm -1 1204 cm -1 1318cm -1 1414 cm -1 1603 cm -1 and 1631 cm -1 The spectral signal intensity near each wavenumber is characteristic of styrene, and the wavenumber positions include, but are not limited to, 500-530 cm⁻¹. -1 Spectral range, 550-570cm -1 Spectral bands, and 787 cm -1 1005 cm -1 1031 cm -1 and 1211 cm -1 The spectral signal intensity near each wavenumber is characteristic of toluene; the wavenumber positions include, but are not limited to, 550-600 cm⁻¹. -1 Spectral range, 850-900 cm -1 Spectral bands, and 1289 cm -1 1415 cm -1 and 1611 cm -1 The spectral signal intensity near each wavenumber is characteristic of acrylonitrile.

[0016] The beneficial effects of this invention are as follows: By employing an online analysis system based on Raman spectroscopy, this invention quantifies the differences in Raman characteristic peaks generated by different contents of olefin mixtures in the ABS circulating solvent of the bulk method according to spectral characteristics. This can accurately and effectively highlight the characteristic signals of olefin mixtures, and monitor the olefin content in the olefin mixture according to the established model, so as to quickly monitor the olefin content in real time and quickly prompt, investigate and repair abnormal content situations, thereby ensuring that ABS production efficiency meets the standards. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 Flowchart of emulsion grafting-bulk SAN blending process; Figure 2 This is a flow chart of the continuous bulk ABS process. Figure 3This is a flowchart of the method of the present invention; Figure 4 The original Raman spectrum of the ABS recycled solvent; Figure 5 The Raman spectrum of ABS after pretreatment with recycled solvent; Figure 6 The figures show a comparison between the Raman model estimates and the corresponding manual analysis values ​​of each component of the ABS circulating solvent. Specifically, a is a comparison between the Raman model estimates and the corresponding manual analysis values ​​of styrene, b is a comparison between the Raman model estimates and the corresponding manual analysis values ​​of acrylonitrile, and c is a comparison between the Raman model estimates and the corresponding manual analysis values ​​of toluene. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solutions in the embodiments of this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art should fall within the protection scope of the embodiments of this application.

[0020] The present invention will now be described in detail with reference to the accompanying drawings. Unless otherwise specified, the features of the following embodiments and implementations can be combined with each other.

[0021] like Figure 3 As shown in the figure, this invention provides an online detection method for the olefin monomer content in the circulating solvent of an ABS production process, comprising the following steps: (1) Construct an online detection system for olefin monomer content at the detection site of the circulating solvent process, including a laser, a spectrometer and signal communication equipment.

[0022] (2) The original optical signal of the mixture of olefin monomers such as SM and AN that enters the circulation loop after the main polymerization reaction is collected by the online detection system described in step (1), and the signal is converted into a digital electrical signal to obtain the original spectral signal of different monomer mixtures.

[0023] (3) Perform preprocessing operations on the original spectral signal described in step (2), including noise suppression, spectral signal smoothing, signal baseline correction, and spectral signal enhancement processing based on the characteristics of various monomers in the monomer mixture.

[0024] (4) By analyzing the different signal intensities of different spectral bands of the pretreated olefin mixture, new olefin features are sought and spectral signal features are analyzed. The correlation between the signal intensity of each spectral band and the olefin content is obtained. The spectral feature positions corresponding to the spectral bands with a high correlation between signal intensity and content are selected and adopted to construct a mathematical feature model of spectral signal intensity and olefin monomer content.

[0025] (5) Measure the spectrum of the olefin monomer mixture sample to be tested, and perform spectral signal enhancement processing including noise suppression, spectral signal smoothing, signal baseline correction and spectral signal enhancement based on the characteristics of various monomers in the monomer mixture. Input the pre-processed spectrum of the olefin monomer mixture sample to be tested into the feature model constructed in step (4) and output the content of each olefin monomer in the sample to be tested.

[0026] The olefin monomer mixture is a mixture of reaction raw materials in the ABS production unit, and the olefin content varies in different olefin mixtures.

[0027] As a preferred embodiment, the present invention has conducted the following specific experiments based on the online detection method for the olefin monomer content in the circulating solvent of the ABS production process. The examples used styrene at a concentration of 400-500 cm³. -1 Spectral characteristic peaks, toluene 500-530 cm⁻¹ -1 Spectral characteristic peaks and acrylonitrile 550-600 cm⁻¹ -1 Taking the characteristic peaks of the spectral band as an example, considering that the mixture contains aromatic components, toluene is used to replace the aromatic components in the experimental study, including the following steps: Step 1: Based on samples from the bulk ABS production process unit, this invention specifically collected a total of 48 samples from a series of circulating solvent process sections. The circulating solvents mainly include styrene (SM), acrylonitrile (AN), and toluene (TOL).

[0028] Step 2: Measure the Raman spectrum of the sample described in Step 1. The Raman spectrometer used is an OceanOptics QE65000 grating spectrometer with an optical resolution of 6 cm⁻¹. -1 A laser with a center wavelength of 785nm was used as the excitation source, and the detection range was 400-2200cm. -1 For all samples, three consecutive measurements were taken, and the average of the three measurements was taken as the Raman spectroscopy result for that sample in this measurement.

[0029] Step 3: To avoid interference from factors such as measurement noise, background fluorescence, and changes in excitation light source intensity, the Raman spectrum measured in Step 2 is preprocessed, mainly including: Step 3.1, Spectral noise suppression: A smoothing filter method is used, with the filter window width set to 150cm.-1 .

[0030] Step 3.2, Signal Baseline Correction: A polynomial baseline correction method is used to obtain a fitted baseline by optimizing the parameters of the linear baseline; the fitted baseline is then subtracted from the Raman spectrum to eliminate fluorescence background interference.

[0031] in, Figure 4 and Figure 5 The images show the original Raman spectra and the pre-processed Raman spectra of the cyclic solvent sample, with wavenumber positions in the range of 500-530 cm⁻¹. -1 The spectral signal intensity in this band exhibits characteristic variations of toluene. The wavenumber position is located at 550-600 cm⁻¹. -1 The spectral signal intensity of the spectral band reflects the characteristic changes in acrylonitrile. Therefore, the styrene content can be obtained by subtracting the contents of the two components mentioned above. It is evident that after signal preprocessing, the two characteristic spectral bands exhibit more pronounced differences, allowing for accurate modeling with the contents of each component in the corresponding cyclic solvent.

[0032] The statistical results of the errors for each sample are shown in Table 1.

[0033] Table 1: Statistical results of errors in the content of each component in 48 cyclic solvent samples .

[0034] Of the 48 test samples, the mean square error (MSE) for styrene was ≤0.27%, for acrylonitrile it was ≤0.16%, and for toluene it was ≤0.2%. Figure 6 The AC plot shows a clear comparison between the Raman predicted values ​​and the manually analyzed values. The content detection results for all 48 samples are shown in Table 2.

[0035] Table 2: Test data of the content of each component in all 48 cyclic solvent samples (all percentages %) .

[0036] The experimental results above show that: 1. For olefin monomers and aromatic solvents in circulating solvents, the accuracy of Raman spectroscopy has a mean square error of ≤0.27%, and it provides a high degree of assurance for the range of maximum and minimum error values, which can meet the requirements of actual production.

[0037] 2. Although the above analysis is a Raman quantitative analysis method for a mixture of three components, styrene, acrylonitrile and toluene, since this method is based entirely on the characteristic vibrational peaks of olefins and aromatics, it is also applicable to the online detection of other mixtures of olefins and aromatics.

[0038] 3. As a non-contact in-situ detection technology, Raman spectroscopy also has advantages such as fast detection speed (detection time ≤ 1 min), no on-site maintenance, and no need for routine model calibration. Furthermore, since the on-site detection unit does not contain electrical components and only involves optical components (including Raman optical cables), it has strong resistance to electromagnetic interference. Therefore, there are no other engineering application issues.

[0039] 4. Online measurement and characteristic analysis of Raman spectroscopy provides a new, safe, efficient and accurate method for online detection of olefin monomer content in the circulating solvent of ABS production process.

[0040] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only.

[0041] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. An online detection method for the olefin monomer content in the circulating solvent of an ABS production process, characterized in that, Includes the following steps: (1) Construct an online detection system for olefin monomer content at the detection point of the circulating solvent process, including a laser, a spectrometer and signal communication equipment; (2) The original optical signal of the olefin monomer mixture that enters the circulation loop after the main polymerization reaction is collected by the online detection system, and the signal is converted into a digital electrical signal to obtain the original spectral signal of different monomer mixtures; (3) Preprocess the original spectral signal; (4) Combine the Raman spectra of the pure component standard substances in the circulating solvent to find new olefin features and perform spectral signal feature analysis. By analyzing the different signal intensities of different spectral bands of the pretreated olefin mixture, the correlation between the spectral signal intensity distribution and the olefin content is analyzed. The spectral bands with a high correlation between signal intensity and content are selected and the consistency of the spectral feature positions corresponding to the selected olefin features is verified. A mathematical feature model of spectral signal intensity and olefin monomer content is constructed. (5) Measure the spectrum of the olefin monomer mixture sample to be tested, perform preprocessing, input the preprocessed spectrum of the olefin monomer mixture sample to be tested into the feature model constructed in step (4), and output the content of each olefin monomer in the sample to be tested.

2. The online detection method for olefin monomer content in the circulating solvent of the ABS production process according to claim 1, characterized in that, Step (1) includes: using an excitation wavelength of 785nm and a detection range of 400-2200cm. -1 A laser was used to perform Raman spectroscopy analysis on an olefin mixture.

3. The online detection method for olefin monomer content in the circulating solvent of the ABS production process according to claim 1, characterized in that, The olefin monomer mixture is a mixture of reaction raw materials in the ABS production unit, containing aromatic hydrocarbons and olefin monomers.

4. The online detection method for olefin monomer content in the circulating solvent of the ABS production process according to claim 1, characterized in that, The preprocessing of the spectral signal includes noise suppression, spectral signal smoothing, signal baseline correction, and spectral signal enhancement based on the characteristics of various monomers in the monomer mixture.

5. The online detection method for olefin monomer content in the circulating solvent of the ABS production process according to claim 1, characterized in that, The spectral signal feature analysis specifically involves combining the method of selecting the mechanistic characteristic peaks of the standard Raman spectrum of pure components with the method of performing correlation analysis on the actual acquired spectra to obtain features that conform to the theoretical characteristic spectral bands of each component and the correlation between the actual measured spectra and the content.

6. The online detection method for olefin monomer content in the circulating solvent of the ABS production process according to claim 1, characterized in that, The novel olefin features include: wavenumber positions ranging from 400-500 cm⁻¹. -1 Spectral range, 600-650 cm -1 Spectral range, 750-800 cm -1 Spectral bands, and 1001 cm -1 1034 cm -1 1183 cm -1 1204 cm -1 1318 cm -1 1414 cm -1 1603cm -1 and 1631 cm -1 The spectral signal intensity near each wavenumber is characteristic of styrene, with wavenumber positions including 500-530 cm⁻¹. -1 Spectral range, 550-570cm -1 Spectral bands, and 787 cm -1 1005 cm -1 1031 cm -1 and 1211 cm -1 The spectral signal intensity near each wavenumber is characteristic of toluene; the wavenumber positions include 550-600 cm⁻¹. -1 Spectral range, 850-900 cm -1 Spectral bands, and 1289 cm -1 1415 cm -1 and 1611 cm -1 The spectral signal intensity near each wavenumber is characteristic of acrylonitrile.

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