Conversion rate control method and system for low molecular weight aromatic trimer curing agents

Abstract

This application relates to the field of isocyanate curing agent synthesis technology, specifically to a method and system for controlling the conversion rate of a low molecular weight aromatic trimer curing agent. The method elevates the TDI monomer conversion rate from an endpoint detection index to a real-time control variable. The NCO concentration is monitored in real time by ATR-FTIR and converted into TDI monomer conversion rate. Combined with staged control and the use of an endpoint prediction model for advance preparation, the polymerization inhibitor is automatically injected when the conversion rate reaches the target, thereby improving the control accuracy of the reaction endpoint. The relative standard deviation of TDI monomer conversion rate between batches can be reduced to below 4.0%.

Description

Technical Field

[0001] This application relates to the field of isocyanate curing agent synthesis technology, specifically to a method and system for controlling the conversion rate of a low molecular weight aromatic trimer curing agent. Background Technology

[0002] Low molecular weight aromatic trimer curing agents (represented by TDI trimer curing agents) are key components in polyurethane coatings and adhesives. Curing agents prepared from toluene diisocyanate (TDI) via trimerization, with isocyanurate trimer as the main component (trimer content ≥70wt%), have a number average molecular weight not exceeding 800 Da and contain almost no pentamers or higher polymers with a molecular weight exceeding 1500 Da. The six-membered ring structure of isocyanurate endows the product with high functionality, a high thermal decomposition temperature (up to approximately 400℃), and excellent rigidity. When combined with hydroxyl components, it can rapidly crosslink to form a film with high crosslinking density, high hardness, good adhesion, and excellent thermal stability.

[0003] However, the production of TDI trimer curing agents faces the problem of insufficient conversion rate control precision. The trimer reaction process is difficult to judge accurately in real time, leading to large fluctuations in free TDI content between batches, unstable viscosity, and NCO content deviating from the target range. Because the NCO terminal groups of the trimer still possess reactivity, further reactions towards pentamers, heptamers, and polymers are inevitable during the reaction process, causing an increase in product viscosity. Simultaneously, the traditional NCO titration method has a long detection cycle (CN105001401A), which cannot meet the needs of real-time monitoring. In production, the reaction time is often excessively extended to ensure that free TDI meets the standard, resulting in excessively large trimer molecular weight, excessive product viscosity, and decreased solvent tolerance, making it difficult to simultaneously meet the dual requirements of environmental protection (low free TDI) and high performance. Summary of the Invention

[0004] The purpose of this invention is to provide a conversion rate control method and system for low molecular weight aromatic trimer curing agents, in order to solve the technical problems in the prior art, such as inaccurate TDI monomer conversion rate control, large deviation of NCO endpoint concentration, and poor batch stability caused by detection lag and ring-opening control, and to achieve free TDI < 0.5%, NCO endpoint concentration deviation ≤ ±0.3%, and batch-to-batch relative standard deviation < 4%.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following solution: A method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent, comprising the following steps: S1, aromatic diisocyanate monomer and solvent are added to the reaction vessel, and the initial NCO concentration is calculated based on the amount of materials added. And set the target conversion rate of TDI monomers. and the corresponding NCO endpoint concentration ; S2, Infrared spectra are continuously collected in the reaction solution obtained in step S1 to obtain the characteristic peak intensities of the NCO group, and the current NCO concentration is calculated in real time based on the pre-established standard curve of NCO concentration versus peak area. According to real-time monitoring The catalyst is added in batches to the reaction system, while simultaneously... Converted to current TDI monomer conversion rate ; S3, Current TDI monomer conversion rate ≥TDI monomer target conversion rate When the reaction proceeds, it enters the termination stage; an inhibitor is automatically added to terminate the reaction.

[0006] Furthermore, the batch addition amounts of the catalyst include the following: The first batch consists of 20% to 30% of the total catalyst added at the start of the reaction. The second batch of NCO concentrations under real-time monitoring Reduced to the initial NCO concentration When the concentration is 80% to 85%, add 30% to 40% of the total catalyst. The third batch of NCO concentrations under real-time monitoring Reduced to the initial NCO concentration Add the remaining catalyst when it reaches 60% to 65% of its capacity.

[0007] Furthermore, the current TDI monomer conversion rate The conversion formula is: Simultaneously calculate the rate of change of TDI monomer conversion. ;in Let be the TDI monomer conversion rate for the i-th iteration. The TDI monomer conversion rate for the (i-1)th iteration is... This is the sampling interval.

[0008] Furthermore, the current TDI monomer conversion rate <TDI monomer target conversion rate At that time, the following phased control measures will be implemented: When 0≤ When <20%, monitor If the rate falls below the preset lower limit, the catalyst will be automatically replenished. When 20%≤ When the concentration is <60%, a PID control module is used to adjust the reaction temperature. Maintain within the preset stable rate value; When 60%≤ < At that time, increase the sampling frequency to once every 15 seconds to predict arrival. Remaining time ,when Enter the pre-termination state when ≤2min.

[0009] Furthermore, The calculation formula is: ; This is a correction coefficient that is dynamically adjusted based on the deviation between the actual rate and the predicted rate in the first 10 minutes, with a value range of 0.8 to 1.2.

[0010] Furthermore, the preset rate lower limit is 2% / h to 5% / h; the preset rate stability value is 8% / h to 12% / h.

[0011] Furthermore, the moisture content of the reaction system in step S1 is ≤200ppm; the sampling frequency in step S2 is 30s~60s.

[0012] Furthermore, step S2 also includes using an online ultraviolet spectrophotometer to detect the concentration of free TDI monomer in the reaction solution in real time, establishing a standard curve of mass concentration versus ultraviolet absorbance, and using the free TDI concentration ≤1.2% as a supplementary condition for auxiliary triggering termination.

[0013] A conversion control system for a low molecular weight aromatic trimer curing agent, comprising: Data acquisition unit: includes an in-situ ATR-FTIR spectral probe and a temperature sensor inserted into the reaction vessel, used to acquire NCO spectral data and reaction temperature in the reaction system in real time; Conversion rate calculation and control unit: Connected to the data acquisition unit, it has a built-in standard curve of NCO concentration and peak area and an endpoint prediction module, used to calculate the TDI monomer conversion rate in real time based on the acquired NCO spectral data. and the rate of change in TDI monomer conversion ,according to The system performs phased control at each stage and issues a termination command when it determines that the preset target conversion rate has been reached. The execution unit, connected to the conversion calculation and control unit, includes an automatic drip pump for trimerizing catalyst, a jacketed temperature control valve, and an automatic injection device for polymerization inhibitor, used to automatically add catalyst and inject polymerization inhibitor according to control commands.

[0014] Furthermore, the data acquisition unit also includes an online ultraviolet spectrophotometer detection module for real-time quantitative determination of free TDI monomer concentration.

[0015] The beneficial effects of this invention are as follows: By monitoring NCO concentration in real time using ATR-FTIR and converting it to TDI monomer conversion rate, combined with staged control, the control accuracy of the reaction endpoint is improved, and the relative standard deviation of TDI monomer conversion rate between batches can be reduced to below 4.0%.

[0016] In the later stages of the reaction, the remaining time to reach the target conversion rate is predicted. When the time is ≤2 minutes, the reaction enters a pre-termination state to avoid overshooting or undershooting in the later stages of the reaction, thereby improving the stability of the final free TDI content in the final product. Attached Figure Description

[0017] Figure 1 This is a process flow diagram of the control method of the present invention. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0019] A method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent, referring to... Figure 1 This includes the following steps: S1, add aromatic diisocyanate (TDI) and solvent to the reaction vessel, controlling the moisture content of the reaction system to ≤200ppm (ensuring that NCO is not consumed). Calculate the initial NCO concentration based on the amount of materials added. = (Initial molar number of TDI monomers × Number of NCO groups per TDI molecule × Molar mass of NCO groups) / Total mass of the reaction system; and set the target conversion rate of TDI monomers. and the corresponding NCO endpoint concentration .

[0020] S20, based on real-time monitored NCO concentration The catalyst was added to the reaction system in batches to obtain the reaction solution; Traditional processes involve adding all the catalyst at once, which leads to intense exothermic reactions in the early stages of the reaction and a decline in catalyst activity in the later stages. Therefore, it is necessary to extend the reaction time to reduce free TDI.

[0021] The catalyst is added in batches as follows: The first batch is added at the beginning of the reaction, consisting of 20% to 30% of the total catalyst, to ensure initiation. The total amount is controlled to prevent runaway reactions. The second batch of NCO concentrations under real-time monitoring Reduced to the initial NCO concentration When the catalyst reaches 80% to 85% of its total volume, add 30% to 40% of the total catalyst. At this point, the reaction has stabilized. Adding new catalyst can maintain a high reaction rate and shorten the later stage time. The third batch of NCO concentrations under real-time monitoring Reduced to the initial NCO concentration The remaining catalyst is added when the concentration is 60% to 65% to maintain a sufficiently high catalyst concentration in the high conversion stage (diffusion control zone) so that free TDI can be continuously consumed to the target level.

[0022] S21. An in-situ ATR-FTIR spectral probe is inserted into the reaction solution to continuously acquire infrared spectra at a sampling frequency of 30-60 s. The principle of total internal reflection is used to measure the liquid in contact with the probe surface, unaffected by bubbles or particles. The NCO stretching vibration peak at 2270 cm⁻¹ is very strong and does not overlap with the peaks of the solvent (ethyl acetate, butyl acetate), ensuring accurate quantification. This allows for the acquisition of the characteristic peak intensity of the NCO group in the reaction solution, establishing a standard curve of NCO concentration versus peak area, and real-time calculation of the current NCO concentration. And converted to the current TDI monomer conversion rate. .

[0023] Current TDI monomer conversion rate The conversion formula is: Simultaneously calculate the rate of change of TDI monomer conversion. ;in Let be the TDI monomer conversion rate for the i-th iteration. The TDI monomer conversion rate for the (i-1)th iteration is... This is the sampling interval.

[0024] It should be noted that in this invention The unified representation is the current NCO concentration calculated in real time using ATR-FTIR spectroscopy. This value is used both to determine the threshold for batch catalyst addition and to calculate the current TDI monomer conversion rate. ; This indicates the initial NCO concentration calculated based on the feed amount; This indicates the preset NCO endpoint concentration.

[0025] S22. The concentration of free TDI monomer in the reaction solution was detected in real time using an online ultraviolet spectrophotometer. A standard curve of mass concentration versus ultraviolet absorbance was established. When the concentration of free TDI is ≤1.2%, it is used as a supplementary condition for auxiliary triggering termination.

[0026] It should be noted that ATR-FTIR measures total NCO and cannot directly distinguish between free TDI and NCO in the polymer. Ultraviolet spectrophotometry (UV-Vis) can quantify free TDI. Using it as an auxiliary trigger condition improves the reliability of conversion control.

[0027] S3, Determine the current TDI monomer conversion rate TDI monomer target conversion rate The following phased control is implemented based on the relationship between them: When 0≤ When <20%, monitor If the rate is lower than the preset lower limit of 2% / h~5% / h, the catalyst will be automatically added. When the catalyst comes into contact with TDI, the trimerization reaction has just started, and the NCO decreases slowly. When 20%≤ When the concentration is <60%, a PID control module is used to adjust the reaction temperature to ensure that... Maintaining a preset stable rate of 8% / h to 12% / h, the reaction enters a stable self-accelerating stage, with a large amount of trimer being generated and the system viscosity gradually increasing. At this point, the conversion calculation and control unit activates the PID control module to precisely control the reaction temperature within a preset range (e.g., 70±2℃) by adjusting the flow rate of cooling water or heating medium in the reaction vessel jacket. Maintain a constant rate to keep the reaction in a stable phase; prevent the reaction rate from deviating from the set range, which could lead to overshoot or undershoot in the later stages of the reaction. When 60%≤ < At that time, increase the sampling frequency to once every 15 seconds to predict arrival. Remaining time ,in, The calculation formula is: ; This is a correction coefficient dynamically adjusted based on the deviation between the actual and predicted rates in the first 10 minutes, with a value range of 0.8 to 1.2; when When the time is ≤2 minutes, the system automatically reduces the stirring speed (to reduce shear heat) and pre-pressurizes the polymerization inhibitor pipeline, entering the pre-termination state.

[0028] when ≥ When the reaction proceeds, it enters the termination stage; an inhibitor is automatically added to terminate the reaction.

[0029] The reason for setting up phased control is that trimerization is not a constant-rate process; its kinetic curve is S-shaped: it is slow in the early stage, accelerates in the middle stage, and may experience a sudden change in rate in the later stage due to the decrease in monomer concentration and the increase in system viscosity.

[0030] S4, after the termination program starts, the control system injects a polymerization inhibitor (phosphoric acid, methyl p-toluenesulfonate, or acetyl chloride, in an amount 1.5 to 2.0 times the molar amount of catalyst) into the reaction vessel. Simultaneously, the cooling jacket is fully opened for rapid cooling to ≤50°C, and stirring continues for 30 minutes to ensure complete catalyst deactivation. The polymerization inhibitor injection uses a combination of a fast-opening solenoid valve and a metering pump, with a response time ≤1 second.

[0031] S5, under reduced pressure, heat distillation to remove residual free TDI monomer (can be reduced to below 0.3%), add solvent to adjust to the target solid content (e.g., 50% or 75%), filter and package.

[0032] A conversion control system for a low molecular weight aromatic trimer curing agent, comprising: The data acquisition unit includes an in-situ ATR-FTIR spectral probe and a temperature sensor inserted into the reaction vessel for real-time acquisition of NCO spectral data and reaction temperature in the reaction system. The data acquisition unit also includes an online ultraviolet spectrophotometer detection module for real-time quantitative determination of free TDI monomer concentration.

[0033] Conversion rate calculation and control unit: Connected to the data acquisition unit, it has a built-in standard curve of NCO concentration and peak area and an endpoint prediction module, used to calculate the TDI monomer conversion rate in real time based on the acquired NCO spectral data. and the rate of change in TDI monomer conversion ,according to The system performs phased control at each stage and issues a termination command when it determines that the preset target conversion rate has been reached. When 20%≤ When the concentration is <60%, a PID control module is used to adjust the reaction temperature to ensure that... Maintain the preset stable rate within 8% / h~12% / h; when 60% ≤ < When, the predicted arrival When the remaining time is ≤2 minutes, enter the pre-termination state; when ≥ When the reaction is complete, the reaction enters the termination stage; an inhibitor is automatically added to terminate the reaction, and at the same time, the jacket temperature control valve is fully opened for rapid cooling.

[0034] The execution unit, connected to the conversion calculation and control unit, includes an automatic drip pump for trimerizing catalyst, a jacketed temperature control valve, and an automatic injection device for polymerization inhibitor, used to automatically add catalyst and inject polymerization inhibitor according to control commands; however, this is prior art and will not be described in detail here.

[0035] Example 1 Low molecular weight aromatic trimer curing agent was prepared using the above control method.

[0036] (1) Add 100 kg of aromatic diisocyanate (TDI) and 100 kg of ethyl acetate to the reaction vessel under nitrogen protection. The moisture content should be ≤150 ppm. Calculate the initial NCO concentration based on the amount of material added. =24%, set the target conversion rate for TDI monomers. =70%, corresponding to the NCO endpoint concentration =7.5±0.2% (before dilution).

[0037] (2) Catalyst added in batches: first batch 0.02 kg (25%); second batch 0.03 kg (38%) at NCO concentration Add when the concentration drops to 19.2% (80% of the initial 24%); the third batch of 0.03 kg (37%) was added at the NCO concentration. Add when it drops to 14.4% (initially 60%).

[0038] (3) ATR-FTIR samples are taken every 45 seconds to obtain the characteristic peak intensity of NCO groups in the reaction solution at 2270 cm⁻¹, and a standard curve of NCO concentration versus peak area is established to calculate the current NCO concentration in real time. And converted to the current TDI monomer conversion rate. , When the concentration is 53%, the PID control module sets the temperature to 70±2℃. The preset stable rate value is 10% / h.

[0039] when Once the sampling rate reaches 60%, the sampling frequency is increased to 15 seconds per sampling. When the stirring time is less than 2 minutes, the stirring speed is automatically reduced to 50 rpm to pre-compress the phosphate polymerization inhibitor pipeline.

[0040] when Upon reaching 70%, the solenoid valve opens, injecting 0.6 mol of phosphoric acid within 0.8 seconds, while simultaneously activating the cooling water. After 5 minutes, the NCO concentration stops decreasing. The temperature is then lowered to 45°C, and residual NCO is removed by vacuum distillation (free TDI decreases from 0.8% to 0.2%). Ethyl acetate is added to bring the solid content to 50%, and the mixture is filtered.

[0041] Product testing: Free TDI = 0.21%, NCO endpoint concentration = 7.52%, xylene tolerance = 4.5, viscosity increase < 10% after 7 days of storage at 50℃, RSD = 3.8% (5 consecutive batches); the number average molecular weight of the trimer component is not higher than 800 Da, which meets the low molecular weight requirements.

[0042] Example 2 Low molecular weight aromatic trimer curing agent was prepared using the above control method.

[0043] (1) Add 100 kg of aromatic diisocyanate (TDI) and 24 kg of ethyl acetate to a reaction vessel under nitrogen protection. The moisture content should be ≤180 ppm. Calculate the initial NCO concentration based on the amount of material added. =38.85%, set the target conversion rate for TDI monomers. =80%, corresponding to the NCO endpoint concentration =7.8±0.2% (before dilution).

[0044] (2) Add catalyst in batches: first batch 0.0225 kg (25%); second batch 0.0315 kg (35%), at NCO concentration Add when the concentration drops to 31.08% (initially 80%); the third batch of 0.03 kg (37%) was added at an NCO concentration of... Add when it drops to 23.31% (from the initial 60%).

[0045] (3) ATR-FTIR samples are taken every 40 seconds to obtain the characteristic peak intensity of NCO groups in the reaction solution at 2270 cm⁻¹, and a standard curve of NCO concentration versus peak area is established to calculate the current NCO concentration in real time. And converted to the current TDI monomer conversion rate. , When the concentration is 53%, the PID control module sets the temperature to 70±2℃. The preset stable rate value is 10% / h.

[0046] when Once the sampling rate reaches 60%, the sampling frequency is increased to 15 seconds per sampling. When the stirring time is less than 2 minutes, the stirring speed is automatically reduced to 50 rpm to pre-compress the phosphate polymerization inhibitor pipeline.

[0047] when Upon reaching 80%, the solenoid valve opens, injecting 0.6 mol of phosphoric acid within 0.9 seconds, while simultaneously activating the cooling water. After 5 minutes, the NCO concentration stops decreasing. The temperature is then lowered to 48°C, and residual NCO is removed by vacuum distillation (free TDI decreases from 0.8% to 0.2%). Ethyl acetate is added to bring the solid content to 50%, and the mixture is filtered.

[0048] Product testing: Free TDI = 0.15%, NCO endpoint concentration = 7.78%, xylene tolerance = 3.2, viscosity increase < 10% after 7 days of storage at 50℃, RSD = 4.0% (5 consecutive batches); the number average molecular weight of the trimer component is not higher than 800 Da, which meets the low molecular weight requirements.

[0049] Comparative example (using CN103509170A method, offline control) The feeding and formulation are the same as in Example 1, but offline titration is used to monitor NCO (sampled every 30 minutes), and the operator manually adds the polymerization inhibitor when the NCO is close to the target value.

[0050] Results: In five consecutive batches, the free TDI fluctuated between 0.6% and 1.8%, the NCO final concentration fluctuated between 6.5% and 8.5%, the viscosity fluctuated between 500 and 1500 cp, and the RSD between batches was >15%.

[0051] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method of controlling conversion of a low molecular weight aromatic trimer curative, characterized by, Includes the following steps: S1, aromatic diisocyanate monomer and solvent are put into the reaction vessel, and the initial NCO concentration is calculated according to the amount of the charge , and the target conversion rate of TDI monomer is set , and the corresponding end NCO concentration ; S2, continuously collecting infrared spectrum in the reaction solution obtained in step S1, obtaining characteristic peak intensity of NCO group, and calculating current NCO concentration according to pre-established NCO concentration and peak area standard curve ; according to the real-time monitored value, adding catalyst in batches in the reaction system, and simultaneously converting into current TDI monomer conversion rate ; S3, current TDI monomer conversion ≥TDI monomer target conversion When, enter the termination phase; automatically add a polymerization inhibitor to terminate the reaction.

2. The method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent according to claim 1, characterized in that, The catalyst is added in batches as follows: The first batch consists of 20% to 30% of the total catalyst added at the start of the reaction. The second batch of NCO concentrations under real-time monitoring Reduced to the initial NCO concentration When the concentration is 80% to 85%, add 30% to 40% of the total catalyst. The third batch of NCO concentrations under real-time monitoring Reduced to the initial NCO concentration Add the remaining catalyst when it reaches 60% to 65% of its capacity.

3. The method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent according to claim 1, characterized in that, Current TDI monomer conversion rate The conversion formula is: ; Simultaneously calculate the rate of change of TDI monomer conversion. ;in Let be the TDI monomer conversion rate for the i-th iteration. The TDI monomer conversion rate for the (i-1)th iteration is... This is the sampling interval.

4. The method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent according to claim 3, characterized in that, Current TDI monomer conversion rate <TDI monomer target conversion rate At that time, the following phased control measures will be implemented: When 0≤ When <20%, monitor If the rate falls below the preset lower limit, the catalyst will be automatically replenished. When 20%≤ When the concentration is <60%, a PID control module is used to adjust the reaction temperature to ensure that... Maintain within the preset stable rate value; When 60%≤ < At that time, increase the sampling frequency to once every 15 seconds to predict arrival. Remaining time ,when Enter the pre-termination state when ≤2min.

5. The method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent according to claim 4, characterized in that, The calculation formula is: ; This is a correction coefficient that is dynamically adjusted based on the deviation between the actual rate and the predicted rate in the first 10 minutes, with a value range of 0.8 to 1.

2.

6. The method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent according to claim 4, characterized in that, The preset lower limit of the rate is 2% / h to 5% / h; the preset stable rate is 8% / h to 12% / h.

7. The method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent according to claim 1, characterized in that, The moisture content of the reaction system in step S1 is ≤200ppm; the sampling frequency in step S2 is 30s~60s.

8. The method for controlling the conversion rate of a low molecular weight aromatic trimer curing agent according to claim 1, characterized in that, Step S2 also includes using an online ultraviolet spectrophotometer to detect the concentration of free TDI monomer in the reaction solution in real time, establishing a standard curve of mass concentration versus ultraviolet absorbance, and using the free TDI concentration ≤1.2% as a supplementary condition for triggering termination.

9. A conversion rate control system for a low molecular weight aromatic trimer curing agent, characterized in that, include: Data acquisition unit: includes an in-situ ATR-FTIR spectral probe and a temperature sensor inserted into the reaction vessel, used to acquire NCO spectral data and reaction temperature in the reaction system in real time; Conversion rate calculation and control unit: Connected to the data acquisition unit, it has a built-in standard curve of NCO concentration and peak area and an endpoint prediction module, used to calculate the TDI monomer conversion rate in real time based on the acquired NCO spectral data. and the rate of change in TDI monomer conversion ,according to The system performs phased control at each stage and issues a termination command when it determines that the preset target conversion rate has been reached. The execution unit, connected to the conversion calculation and control unit, includes an automatic drip pump for trimerizing catalyst, a jacketed temperature control valve, and an automatic injection device for polymerization inhibitor, used to automatically add catalyst and inject polymerization inhibitor according to control commands.

10. The conversion rate control system for a low molecular weight aromatic trimer curing agent according to claim 9, characterized in that, The data acquisition unit also includes an online ultraviolet spectrophotometer detection module for real-time quantitative determination of free TDI monomer concentration.

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