An activation and dehydration system for caprolactam in-situ polymerization

Abstract

The present application relates to the technical field of polymer material polymerization, in particular to a kind of activation and dehydration system of caprolactam in-situ polymerization, including vacuum dehydration activation kettle, the vacuum dehydration activation kettle top is equipped with purging piece and condensing piece, and vacuum dehydration activation kettle inside is equipped with filler layer bin and helical stirring piece, the vacuum dehydration activation kettle side wall is equipped with on-line monitoring module, and vacuum dehydration activation kettle side edge is electrically connected with the distribution cabinet corresponding to on-line monitoring module;It also includes the following steps: S1, raw material input;S2, temperature rising dehydration;S3, synergistic activation;S4, constant temperature storage;The present application is aimed at the technical defects of low efficiency, poor precision, high energy consumption and insufficient product stability of existing step-by-step pretreatment process, through the design of vacuum dehydration activation kettle, multi-module collaborative matching and PLC full-automatic closed-loop control, dehydration and activation process coupling synergy is realized, compared with traditional technology, it has the significant advantages of high efficiency, controllable precision, stable reaction, adaptive mass production and the like.

Description

Technical Field

[0001] This invention relates to the field of polymer polymerization technology, specifically to an activation and dehydration system for in-situ polymerization of caprolactam. Background Technology

[0002] Caprolactam in-situ polymerization technology, with its advantages of short process, high molding efficiency, and excellent mechanical properties of products, is widely used in large-scale industrial production fields such as automotive parts and high-end engineering plastics. This process has extremely high requirements for the moisture content and activation degree of the raw material caprolactam: on the one hand, trace amounts of moisture in the raw material can trigger side reactions, reducing the molecular weight of the polymer and the mechanical properties of the product, and the moisture content is usually required to be <0.02%; on the other hand, the induction period of caprolactam anionic polymerization is relatively long, and it is necessary to introduce acylated active species of caprolactam through activators to shorten the polymerization cycle and improve production efficiency.

[0003] However, existing caprolactam pretreatment processes mostly employ a step-by-step process of dehydration and activation, resulting in fragmented and redundant steps, long overall processing cycles, and high ineffective energy consumption. Traditional equipment lacks precise circulating dehydration structures and online monitoring methods, leading to uneven heating and dehydration of raw materials, making it difficult to stably control low moisture content. Furthermore, activation uniformity is poor, and raw materials are prone to high-temperature oxidation, resulting in weak batch stability. Simultaneously, traditional processes have low automation levels and lack closed-loop precise control capabilities, easily causing problems such as long polymerization induction periods, incomplete reactions, and numerous product molding defects, making them unsuitable for large-scale, high-precision continuous production.

[0004] Therefore, in order to solve the above problems, an activation and dehydration system for in-situ polymerization of caprolactam is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide an activation and dehydration system for in-situ polymerization of caprolactam, so as to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: an activation and dehydration system for in-situ polymerization of caprolactam, comprising a vacuum dehydration activation vessel, wherein the top of the vacuum dehydration activation vessel is equipped with a purging component and a condensing component, and the interior of the vacuum dehydration activation vessel is equipped with a packing layer and a spiral stirring component, wherein the side wall of the vacuum dehydration activation vessel is equipped with an online monitoring module, and the side of the vacuum dehydration activation vessel is electrically connected to a power distribution cabinet corresponding to the online monitoring module;

[0007] It also includes the following steps:

[0008] S1. Raw material input: Add solid caprolactam and activator toluene diisocyanate (TDI) to the vacuum dehydration activation reactor in a certain mass ratio, and start nitrogen purging to remove air from the reactor; the ratio of solid caprolactam (CPL) to activator toluene diisocyanate (TDI) is 100:0.2, and the nitrogen purging time is 5-10 minutes to ensure that the oxygen content in the reactor is ≤0.1%;

[0009] S2, Heating and Dehydration: Heating and vacuuming, the raw material passes through the packing dehydration layer to adsorb moisture, and the steam condensation recovery device collects the by-product water; the temperature inside the vessel is heated to 130℃ with a control accuracy of ±1℃, and vacuumed to -0.09MPa with a control accuracy of ±0.002MPa;

[0010] S3. Synergistic Activation: When the online monitoring module detects that the moisture content of the raw material has dropped to the set value, the temperature inside the reactor is increased and a vacuum state is maintained to allow TDI and CPL to fully react and generate acylated lactam active species; when the online monitoring module detects that the moisture content of the raw material has dropped to <0.01%, the temperature inside the reactor is increased to 140℃, and a vacuum state is maintained for stirring for 15 minutes. The activation degree is monitored in real time every 30 seconds. When the activation degree is detected for ≥98% for 3 consecutive times, the activation is considered complete.

[0011] S4. Constant temperature storage: After activation, reduce the temperature inside the reactor to 100°C, maintain nitrogen protection, and wait for injection.

[0012] Addressing the technical shortcomings of existing step-by-step pretreatment processes, such as low efficiency, poor precision, high energy consumption, and insufficient product stability, this invention achieves coupled and coordinated completion of dehydration and activation processes through a dedicated structural design of a vacuum dehydration and activation kettle, multi-module collaborative matching, and PLC fully automatic closed-loop control. Compared with traditional technologies, it has significant advantages such as high efficiency and energy saving, controllable precision, stable reaction, and suitability for mass production.

[0013] As a further step in this solution, the vacuum dehydration and activation vessel includes an inner vessel cylinder, the packing layer chamber and the spiral agitator are assembled inside the inner vessel cylinder, and a jacketed sleeve is installed around the outer wall of the inner vessel cylinder. The detection components are correspondingly inserted into the outer wall of the inner vessel cylinder and the outer wall of the jacketed sleeve. A base is supported at the bottom of the jacketed sleeve. A loading chamber and a vessel lid are assembled at the top of the inner vessel cylinder. The purging component includes a gas supply tank, and the gas supply tank outlet is connected to one side of the top of the vessel lid via a gas delivery pipe. A condenser is assembled on the other side of the top of the vessel lid, and the bottom of the gas supply tank is supported on the side of the base. The power distribution cabinet is fixedly assembled at the center of the top of the base. The power distribution cabinet integrates a PLC programmable logic controller corresponding to the online monitoring module. A flow regulating valve and a pressure sensor are installed at the gas supply tank outlet. The detection components include a moisture sensor, a temperature sensor and an activation degree detector.

[0014] The above-mentioned technical means facilitate the assembly of the vacuum dehydration and activation kettle. During use, after feeding, air is discharged through the purging component, and steam is condensed and recovered through the condensing component to assist in dehydration. With the cooperation of the spiral agitator and the packing layer, the raw materials are circulated, stirred, lifted and dehydrated. With the cooperation of the jacket, heating and activation are assisted. The online monitoring module and related equipment are used for coordinated processing.

[0015] As a further step of this solution, the bottom of the inner wall of the inner vessel is equipped with an inner bottom support frame corresponding to the packing layer, and a hollow cavity corresponding to the spiral agitator is opened in the center of the packing layer. The packing height of the packing layer is 1 / 2 to 1 / 3 of the inner height of the inner vessel. A rotating rod is integrally fixed inside the spiral agitator, and an upper support frame is mounted on the upper end of the rotating rod through a bearing. The upper support frame is cross-shaped, and the outer end of the upper support frame is fixed in the center of the upper loading chamber. The top of the rotating rod is inserted and mounted on the top of the vessel lid through a mechanical seal and extends upward. A motor is connected and mounted on the top of the rotating rod, and the back of the motor is supported and mounted on the top of the vessel lid through a back plate.

[0016] Through the above-mentioned technical means, the raw materials are dehydrated with the help of the packing layer silo, and the spiral agitator is used to stir and lift the materials, so that the raw materials can be easily circulated for dehydration, reducing the moisture content and assisting in subsequent activation.

[0017] As a further improvement of this solution, an inlet pipe is connected to the lower part of one side of the outer wall of the jacket, and an outlet pipe is connected to the upper part of the other side of the outer wall of the jacket. Both the inlet and outlet pipes are curved and extend downward. The jacket is covered with an outer mesh, and reinforcing ribs are evenly fixed in the middle of the outer mesh. An outlet pipe is connected to the bottom of the inner vessel, and a discharge valve is installed at the lower end of the outlet pipe. Feeding pipes are installed on the front and rear sides of the top of the vessel cover, and an air extraction valve is installed on the side of the vessel cover. A pre-slot is also connected to the top of the vessel cover. Plugs are installed on the outside of both the feeding pipe and the pre-slot.

[0018] The above-mentioned technical means are used to protect and isolate the outside of the jacket sleeve, avoid direct contact, make it safer to use, and facilitate the installation and assembly of corresponding equipment and the feeding and discharging of materials.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. By integrating the vacuum dehydration and activation kettle with its internal structure, packing circulation dehydration system and integrated process, the dehydration and activation processes are coupled and completed simultaneously, eliminating redundant processes such as multi-equipment transfer and repeated pressure stabilization and heating. This reduces pretreatment time by 40% and overall energy consumption by 25%. At the same time, relying on the closed-loop flow field and precise temperature and pressure control, the moisture content of the raw materials is stably controlled below 0.01% and the activation degree is ≥98%, thereby significantly improving the accuracy of raw material pretreatment and production efficiency, making it suitable for large-scale continuous production scenarios.

[0021] 2. By incorporating an online multi-parameter monitoring module and a PLC fully automatic closed-loop control system, the entire raw material pretreatment process can be monitored in real time, precisely controlled, and automatically started and stopped. This completely avoids human error and raw material oxidation side reactions, achieving in-situ polymerization without an induction period, shortening the polymerization cycle to 1.8 minutes, resulting in a more complete polymerization reaction and a more uniform molecular weight distribution of the product. This effectively improves the mechanical properties of the product and the yield of molded products, solves the batch quality fluctuation problem of traditional processes, and has excellent mass production stability and engineering promotion value. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the 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.

[0023] Figure 1 This is a schematic diagram of the process flow of the present invention;

[0024] Figure 2 This is a frontal perspective three-dimensional schematic diagram of the overall structure of the present invention;

[0025] Figure 3 This is a bottom-view perspective view of the overall structure of the present invention;

[0026] Figure 4 This is a side-view perspective of a partial structure of the vacuum dehydration and activation vessel of the present invention;

[0027] Figure 5 This is a three-dimensional front view cross-sectional view of a partial structure of the vacuum dehydration and activation vessel of the present invention;

[0028] Figure 6 This is a top-view cross-sectional schematic diagram of a partial structure of the vacuum dehydration and activation vessel of the present invention;

[0029] Figure 7 This is a frontal perspective three-dimensional schematic diagram of a partial structure of the packing layer silo and the spiral agitator of the present invention;

[0030] Figure 8 This is a frontal three-dimensional exploded view of a partial structure of the vacuum dehydration and activation kettle of the present invention.

[0031] In the diagram: 100, Vacuum dehydration and activation kettle; 101, Base; 102, Power distribution cabinet; 110, Inner kettle cylinder; 111, Upper loading chamber; 112, Kettle cover; 113, Discharge pipe; 114, Discharge valve; 115, Feeding pipe; 116, Air extraction valve; 117, Pre-slot; 120, Jacket sleeve; 121, Liquid inlet pipe; 122, Liquid outlet pipe; 130, Packing layer chamber; 131, Inner bottom support frame; 132, Hollow cavity; 140, Spiral agitator; 141, Rotating rod; 142, Upper support frame; 143, Motor; 144, Back plate; 150, Purging component; 151, Air supply tank; 152, Air delivery pipe; 160, Condensation component; 170, Detection component; 180, Outer cover mesh; 181, Reinforcing rib plate. Detailed Implementation

[0032] 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 embodiments of the present invention, and 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.

[0033] Please see Figures 1-8 An embodiment of the present invention provides an activation and dehydration system for in-situ polymerization of caprolactam, comprising a vacuum dehydration activation vessel, wherein the top of the vacuum dehydration activation vessel is equipped with a purging component and a condensing component, and the interior of the vacuum dehydration activation vessel is equipped with a packing layer and a spiral agitator, the side wall of the vacuum dehydration activation vessel is equipped with an online monitoring module, and the side of the vacuum dehydration activation vessel is electrically connected to a power distribution cabinet corresponding to the online monitoring module;

[0034] It also includes the following steps:

[0035] S1. Raw material input: Add solid caprolactam and activator toluene diisocyanate (TDI) to the vacuum dehydration activation reactor in a certain mass ratio, and start nitrogen purging to remove air from the reactor; the ratio of solid caprolactam (CPL) to activator toluene diisocyanate (TDI) is 100:0.2, and the nitrogen purging time is 5-10 minutes to ensure that the oxygen content in the reactor is ≤0.1%; maintain the nitrogen pressure in the reactor at 0.01-0.03 MPa to remove air from the reactor and prevent oxidation of the raw materials;

[0036] S2, Heating and Dehydration: Heating and vacuuming, the raw material passes through the packing dehydration layer to adsorb moisture, and the steam condensation recovery device collects the by-product water; the temperature inside the vessel is heated to 130℃ with a control accuracy of ±1℃, and vacuumed to -0.09MPa with a control accuracy of ±0.002MPa;

[0037] S3. Synergistic Activation: When the online monitoring module detects that the moisture content of the raw material has dropped to the set value, the temperature inside the reactor is increased and a vacuum state is maintained to allow TDI and CPL to fully react and generate acylated lactam active species; when the online monitoring module detects that the moisture content of the raw material has dropped to <0.01%, the temperature inside the reactor is increased to 140℃, and a vacuum state is maintained for stirring for 15 minutes. The activation degree is monitored in real time every 30 seconds. When the activation degree is detected for ≥98% for 3 consecutive times, the activation is considered complete.

[0038] S4. Constant temperature storage: After activation, reduce the temperature inside the reactor to 100°C and maintain nitrogen protection. Wait for injection. At this time, the raw material is in a liquid state with a water content of <0.01% and an activation degree of ≥98%, and can be directly used for subsequent in-situ polymerization reactions.

[0039] As described in more detail in this embodiment, the vacuum dehydration and activation reactor 100 includes an inner reactor cylinder 110, a packing layer chamber 130, and a spiral agitator 140 assembled inside the inner reactor cylinder 110. A jacketed sleeve 120 is fitted around the outer wall of the inner reactor cylinder 110, and a base 101 supports the bottom of the jacketed sleeve 120. Detection components 170 are correspondingly inserted into the outer walls of the inner reactor cylinder 110 and the jacketed sleeve 120. The detection components 170 include a moisture sensor, a temperature sensor, and an activation degree detector. The moisture sensor uses the Karl Fischer coulometric method with a detection accuracy of ≤0.001%, enabling real-time monitoring of the moisture content in the raw materials. The temperature sensor is distributed at different locations inside the reactor, with a monitoring accuracy of ±0.5℃, ensuring temperature uniformity within the reactor. The activation degree detector uses infrared spectroscopy to monitor the content of acylated lactam active species in real time, calculates the activation degree, and has a detection accuracy of ±0.5%, achieving integrated multi-dimensional detection units and real-time acquisition of raw material state data.

[0040] The inner vessel cylinder 110 is topped with a loading chamber 111 and a vessel cover 112. The purging component 150 includes an air supply tank 151, the outlet of which is connected to one side of the top of the vessel cover 112 via an air supply pipe 152. A condenser 160 is mounted on the other side of the top of the vessel cover 112. The condenser 160 uses a low-temperature condensing coil with a condensation temperature set at 5-10℃. It can condense the water vapor volatilized during the dehydration process into liquid water and collect it, preventing moisture from re-entering the raw material system. The outlet of the air supply tank 151 is equipped with a flow meter. The regulating valve and pressure sensor, with the gas supply tank 151 supported at the bottom of the base 101, maintain the nitrogen pressure inside the reactor at 0.01-0.03 MPa, ensuring the oxygen content inside the reactor is ≤0.1%. The electrical control cabinet 102 is fixedly mounted at the top center of the base 101. The cabinet integrates a PLC programmable logic controller (PLC) corresponding to the online monitoring module. The monitoring system built on the PLC enables closed-loop regulation of heating temperature, vacuum level, and stirring rate. The system has a built-in process parameter database, storing optimal process parameter sets for raw materials with different initial moisture contents. Based on real-time data from the online monitoring module, it automatically adjusts the heating power, vacuum pumping rate, and stirring rate to ensure precise and controllable dehydration and activation processes. Simultaneously, the system has data storage and traceability functions, recording the processing parameters and results for each batch of raw materials, facilitating quality traceability.

[0041] As described in more detail in this embodiment, a liquid inlet pipe 121 is connected and installed on the lower part of one side of the outer wall of the jacket sleeve 120, and a liquid outlet pipe 122 is connected and installed on the upper part of the other side of the outer wall of the jacket sleeve 120. Both the liquid inlet pipe 121 and the liquid outlet pipe 122 are bent downwards to connect with the mold temperature controller for auxiliary heating. An outer cover net 180 is provided to cover the outside of the jacket sleeve 120 to help protect the outer wall of the jacket sleeve 120 and prevent direct contact burns. Reinforcing ribs 181 are evenly fixed in the middle of the outer cover net 180. This facilitates auxiliary wrapping and support, as well as auxiliary assembly wiring. The bottom of the inner cylinder 110 is connected to a discharge pipe 113, and the lower end of the discharge pipe 113 is equipped with a discharge valve 114 to assist in subsequent discharge control. The top front and rear sides of the lid 112 are equipped with feeding pipes 115, and the sides of the lid 112 are equipped with air extraction valves 116. The top of the lid 112 is also connected to a pre-slot 117. Both the feeding pipes 115 and the pre-slot 117 are equipped with plugs to facilitate opening and use as needed.

[0042] As described in more detail in this embodiment, the bottom of the inner wall of the inner vessel cylinder 110 is fitted with an inner bottom support frame 131 corresponding to the packing layer 130 for stable support. A hollow cavity 132 corresponding to the spiral agitator 140 is opened in the center of the packing layer 130 to assist in the assembly of the spiral agitator 140 and the stirring and lifting of the raw materials. The packing height of the packing layer 130 is 1 / 3 to 1 / 2 of the internal height of the inner vessel cylinder 110, assisting in dehydration within the vessel. A rotating rod 141 is integrally fixed inside the spiral agitator 140. An upper support frame 142 is mounted on the upper end of the rotating rod 141 via a bearing. The upper support frame 142 is cross-shaped, and its outer end is fixed to... Inside the upper loading chamber 111, at the center, the top of the rotating rod 141 is inserted and mounted on the top of the vessel cover 112 via a mechanical seal and extends upwards. The top of the rotating rod 141 is connected to and mounted with a motor 143. The back of the motor 143 is supported and mounted on the top of the vessel cover 112 via a back plate 144, which realizes the stable hoisting and driving rotation of the spiral agitator 140, making subsequent operations more convenient. During operation, the raw materials are stirred in the vessel by the spiral agitator 140. Under the spiral setting, the raw materials are lifted and lifted through the hollow cavity 132 to the top of the packing layer chamber 130. They then penetrate downwards by gravity, cooperating with dehydration. This process is repeated to achieve efficient dehydration.

[0043] Example 1:

[0044] 1000 kg of solid caprolactam (CPL) raw material with an initial moisture content of 0.12% was processed using the integrated system and method of this invention. The steps are as follows:

[0045] S1. Raw material input: Add 1000 kg of solid caprolactam (CPL) and 2 kg of activator toluene diisocyanate (TDI) to the vacuum dehydration activation reactor in a certain proportion. After closing the reactor lid, start nitrogen purging for 8 minutes until the oxygen content in the reactor drops to 0.08%.

[0046] S2. Heating and Dehydration: The jacketed heating system is activated to heat the reactor to 130℃, and the temperature is stabilized at 130±0.8℃. The vacuum system is activated to evacuate to -0.09MPa, and the vacuum level is stabilized at -0.09±0.001MPa. The stirring speed is set to 60rpm for continuous stirring and dehydration. The online monitoring module displays the change in moisture content in real time. After 35 minutes, the moisture content of the raw material drops to 0.008%.

[0047] S3. Co-activation: Maintain a vacuum state and raise the temperature inside the vessel to 140℃, then stabilize the temperature at 140±0.7℃; continue stirring at 60rpm for 15 minutes, and use the online monitoring module to detect the activation degree every 30 seconds. At the 12th minute, the activation degree was detected three times in succession, and the results were 98.2%, 98.4%, and 98.5%, respectively, indicating that the activation was complete.

[0048] S4. Constant temperature storage: Reduce the temperature inside the vessel to 100℃, maintain the nitrogen pressure at 0.02MPa, and wait for injection.

[0049] The processing time was 58 minutes, a 40.2% reduction compared to the traditional step-by-step process (approximately 97 minutes); energy consumption was approximately 74.5% of the traditional process, a 25.5% reduction; and the actual utilization rate of the activator TDI was 92.3%, a 15.3% increase compared to the traditional process (approximately 77%). The treated raw materials were used for in-situ polymerization, with a polymerization cycle of 1.8 minutes and no significant induction period. The resulting polyamide-6-based FRP components had a fiber content of 56%, no porosity defects, a tensile strength ≥180 MPa, a flexural strength ≥250 MPa, and stable mechanical properties.

[0050] Comparative Example 1:

[0051] 1000 kg of solid caprolactam (CPL) raw material from the same batch was processed using a traditional stepwise process: First, the CPL was placed in a vacuum drying tower and dried for 45 minutes at 130°C and -0.09 MPa until the moisture content dropped to 0.012%. Then, it was transferred to an activation reactor, and 2 kg of toluene diisocyanate (TDI) was added. The mixture was stirred for 20 minutes at 140°C and atmospheric pressure until the activation degree reached 95.2%. The total processing time was 97 minutes, the energy consumption was 134.2% of that in the embodiment of this invention, and the activator utilization rate was 76.8%. When used for in-situ polymerization, the polymerization cycle was 3.2 minutes, with a significant induction period. The tensile strength of the product fluctuated between 150-175 MPa, indicating poor mechanical property stability.

[0052] The above embodiments and comparative examples show that the integrated system and method of the present invention have significant advantages in terms of processing efficiency, energy consumption, activator utilization rate, polymerization cycle and product stability, and can effectively solve the problems existing in the prior art.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. An activation and dehydration system for in-situ polymerization of caprolactam, comprising a vacuum dehydration and activation reactor, characterized in that: The top of the vacuum dehydration and activation kettle is equipped with a purging component and a condensing component, and the inside of the vacuum dehydration and activation kettle is equipped with a packing layer and a spiral agitator. The side wall of the vacuum dehydration and activation kettle is equipped with an online monitoring module, and the side of the vacuum dehydration and activation kettle is electrically connected to a power distribution cabinet corresponding to the online monitoring module. It also includes the following steps: S1. Raw material input: Add solid caprolactam and activator toluene diisocyanate into the vacuum dehydration and activation reactor in the mass ratio, and turn on nitrogen to purge the air in the reactor. S2, Heating and Dehydration: Heating and vacuuming are performed. The raw material passes through the packing dehydration layer to adsorb moisture. The steam condensation and recovery device collects the by-product water. S3, Synergistic Activation: When the online monitoring module detects that the moisture content of the raw material has dropped to the set value, the temperature inside the reactor is increased and a vacuum state is maintained so that TDI and CPL can fully react to generate acylated lactam active species; S4. Constant temperature storage: After activation, lower the temperature inside the reactor, maintain nitrogen protection, and wait for injection.

2. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 1, characterized in that: In step S1, the ratio of solid caprolactam (CPL) to activator toluene diisocyanate (TDI) is 100:0.2, and the nitrogen purging time is 5-10 minutes to ensure that the oxygen content in the reactor is ≤0.1%.

3. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 1, characterized in that: In S2, the temperature inside the vessel is heated to 130℃ with a control accuracy of ±1℃, and the vacuum is drawn to -0.09MPa with a control accuracy of ±0.002MPa.

4. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 1, characterized in that: In step S3, when the online monitoring module detects that the moisture content of the raw material has dropped to <0.01%, the temperature inside the reactor is raised to 140°C, and the mixture is stirred for 15 minutes while maintaining a vacuum state. The activation degree is monitored in real time every 30 seconds. When the activation degree is detected to be ≥98% for three consecutive times, the activation is considered complete.

5. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 1, characterized in that: The vacuum dehydration and activation vessel includes an inner vessel cylinder, the packing layer chamber and the spiral agitator are assembled inside the inner vessel cylinder, and a jacketed sleeve is installed around the outer wall of the inner vessel cylinder. The detection element is correspondingly inserted into the outer wall of the inner vessel cylinder and the outer wall of the jacketed sleeve. A base is supported at the bottom of the jacketed sleeve. A loading chamber and a vessel lid are assembled at the top of the inner vessel cylinder. The purging component includes an air supply tank, and the air outlet of the air supply tank is connected to one side of the top of the vessel lid through an air supply pipe. A condenser is assembled on the other side of the top of the vessel lid, and the bottom of the air supply tank is supported on the side of the base. The power distribution cabinet is fixedly assembled at the center of the top of the base.

6. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 5, characterized in that: The power distribution cabinet is equipped with a PLC programmable logic controller corresponding to the online monitoring module. The gas supply tank outlet is equipped with a flow regulating valve and a pressure sensor. The detection components include a moisture sensor, a temperature sensor and an activity level detector.

7. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 5, characterized in that: The lower part of one side of the outer wall of the jacket is connected to an inlet pipe, and the upper part of the other side of the outer wall of the jacket is connected to an outlet pipe. Both the inlet and outlet pipes are bent and extend downwards.

8. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 5, characterized in that: The bottom of the inner wall of the inner vessel is equipped with an inner bottom support frame corresponding to the packing layer, and a hollow cavity corresponding to the spiral agitator is opened in the center of the packing layer. The packing height of the packing layer is 1 / 2 to 1 / 3 of the internal height of the inner vessel.

9. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 5, characterized in that: The spiral agitator has an integrally fixed rotating rod inside, and the upper end of the rotating rod is fitted with an upper support frame via a bearing. The upper support frame is cross-shaped, and the outer end of the upper support frame is fixed in the center of the upper loading chamber. The top of the rotating rod is inserted and fitted to the top of the vessel lid via a mechanical seal and extends upwards. A motor is connected and fitted to the top of the rotating rod, and the back of the motor is supported and fitted to the top of the vessel lid via a back plate.

10. The activation and dehydration system for in-situ polymerization of caprolactam according to claim 5, characterized in that: The jacket sleeve is covered with an outer mesh, and reinforcing ribs are evenly fixed in the middle of the outer mesh. The bottom of the inner vessel is connected to a discharge pipe, and a discharge valve is installed at the lower end of the discharge pipe. Feeding pipes are installed on the front and rear sides of the top of the vessel lid, and an air extraction valve is installed on the side of the vessel lid. A pre-slot is also connected to the top of the vessel lid. Plugs are installed on the outside of the feeding pipes and the pre-slot.

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