Preparation method of high-strength polycarbonate resin

Abstract

The invention relates to the technical field of high polymer material synthesis, in particular to a high-strength polycarbonate resin preparation method which comprises the following steps: 1, designing a fatigue life oriented monomer ratio; step 2, gradient polymerization of phase state perception: raising the temperature to a temperature T1 corresponding to a viscosity change rate threshold in the first stage, and maintaining until the distillation rate of a byproduct reaches a safety critical value; in the second stage, variable-rate cooling is implemented based on real-time cloud point detection, an end-capping reagent is injected at the critical point temperature T2 of terminal hydroxyl concentration, and the injection rate is linked with the pressure change rate of the reaction kettle; 3, amorphous confinement solid phase tackifying: treating the polymer particles in a moving bed dynamic temperature field, wherein the temperature field range is dynamically set according to the difference value between the glass transition temperature Tg and the crystallization starting temperature Tc; and step 4, performing electric field grading relaxation. Through the technical means of multi-stage temperature control, electric field adjustment, magnetic field orientation and the like, the molecular chain structure of the resin is comprehensively optimized, and the reliability of a final product in long-term use is ensured.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, and in particular to a method for preparing high-strength polycarbonate resin. Background Technology

[0002] Polycarbonate resin is widely used in consumer electronics, automotive parts, and other fields due to its excellent impact strength and transparency. However, when applied to load-bearing structural components of aerospace drones (such as wing joints and landing gear canopies), traditional polycarbonate faces three major technical bottlenecks: Unmanned aerial vehicles (UAVs) endure high-frequency amplitude loads during takeoff, landing, and turbulent environments, requiring materials to possess both high tensile strength (>70 MPa) and resistance to high-cycle fatigue (>10 MPa). 7 (second cycle). However, the molecular chain structure design of existing resins has inherent defects: Excessive stacking of rigid segments: Existing technology uses bisphenol A and bisphenol fluorene copolymerization, which increases the strength to 75MPa, but the elongation at break drops sharply to below 5%, causing microcracks to initiate in the flange root connector under vibration load. Disordered distribution of flexible segments: Existing technologies that introduce polysiloxane segments for toughening result in a decrease in tensile strength of over 30%, failing to meet the aerodynamic load requirements of wing skin. The fundamental reason is that the molecular chain topology fails to achieve an ordered arrangement of rigid and flexible segments, resulting in insufficient resistance to crack propagation.

[0003] In addition, the melt transesterification process for producing high-viscosity resins requires temperatures above 280°C, which leads to two fatal defects: Molecular weight distribution broadening: At high temperatures, transesterification and cleavage reactions coexist, producing low molecular weight fragments (<20,000 g / mol) accounting for 8-15% of the total, which are confirmed by TEM observation to be aggregated at the main chain interface. Uncontrolled degradation of end groups: In a test of a certain type of UAV servo gearbox, the traditional resin experienced stress corrosion cracking in a humid and hot environment due to excessive end carboxyl group concentration (>50ppm), with an average lifespan of less than 2000 hours. These defects became stress concentration sources, inducing early initiation of fatigue cracks under alternating loads.

[0004] Therefore, there is an urgent need for a method to prepare high-strength polycarbonate resin to solve the above problems. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides a method for preparing high-strength polycarbonate resin, comprising the following steps: Step 1: Fatigue life-oriented monomer ratio design: Bisphenol A and fluorenylbisphenol monomers are mixed in a dynamically determined ratio, which is identified by the inflection point of the prepolymer fatigue life increase under axial amplitude load. Step 2: Phase-aware gradient aggregation: The first stage involves heating to the temperature T1 corresponding to the viscosity change rate threshold and maintaining it until the by-product distillation rate reaches a safe critical value. The second stage implements variable-rate cooling based on real-time cloud point detection, and injects the end-capping agent at the critical temperature T2 of the terminal hydroxyl concentration. The injection rate is linked to the rate of change of pressure in the reactor. Step 3: Amorphous confined solid-state thickening: The polymer particles are treated in a moving bed dynamic temperature field, and the temperature field range is dynamically set according to the difference between the glass transition temperature Tg and the crystallization initiation temperature Tc. Step 4: Electric field graded relaxation: Apply the electric field strength in two stages in a high-voltage electric field. The electric field strength in the first stage is taken as the critical value of molecular chain orientation saturation, and the electric field strength in the second stage is taken as the critical value of birefringence shrinking to a preset ratio.

[0006] Preferably, the identification of the inflection point of sudden increase in fatigue life includes: Prepare bisphenol A / fluorenyl bisphenol prepolymers in at least five different ratios; Fatigue life was tested under simulated loads based on the vibration spectrum of a UAV wing. Plot the life-proportion curve and calculate the second derivative. Take the point where the derivative is zero and the left and right sides have opposite signs as the inflection point. The mixing ratio is controlled within the range of the inflection point ratio ± deviation, whereby the deviation is determined by the reciprocal of the radius of curvature of the curve at the inflection point.

[0007] Preferably, the variable-rate cooling method described in step 2 is implemented as follows: When the real-time temperature is higher than the cloud point, the first cooling rate R1 is adopted, and its value is adjusted according to the trend of online laser scattering intensity change: for every set increase in scattering intensity, R1 increases by the corresponding step size. When the real-time temperature is below the cloud point, a second cooling rate R2 is adopted, the value of which is determined by the dielectric loss factor of the polymerization system: within the dielectric loss peak temperature range, R2 is inversely proportional to the loss peak height. The turbidity point is determined by the point of abrupt change in the intensity of scattered light.

[0008] Preferably, the construction of the dynamic temperature field in step 3 includes: The inlet temperature was set to Tg+ΔT1, and ΔT1 was determined by observation using a hot-stage polarizing microscope: when the heating rate was set, the temperature increment was taken to be more than twice the solid phase thickening time of the crystallization induction time. The intermediate temperature is maintained at (Tg+Tc) / 2-ΔT2, and ΔT2 is optimized by the molecular weight growth rate: when the molecular weight growth rate is detected to decrease by online gel permeation chromatography, ΔT2 is adjusted down proportionally. The outlet section is cooled gradually, and the cooling curve matches the polymer free volume shrinkage rate.

[0009] Preferably, the method for observing the crystallization induction time is as follows: The polymer sheet before thickening was placed on a hot table and heated at a constant rate under a nitrogen atmosphere. The occurrence time of crystal nuclei was analyzed using a polarizing microscope video stream. Repeat the test at the target temperature until a stable induction time spectrum is obtained.

[0010] Preferably, the field strength adjustment rule in step 4 is as follows: The first stage field strength E1 is determined by the online birefringence change curve, and is the field strength corresponding to the rate of change dropping to the first proportion of the initial value. The second-stage field strength E2 is determined by monitoring the energy dissipation during the relaxation process, and is taken as the field strength at which the peak dissipation power is reduced to a safe threshold. The timing of field strength switching is determined based on the dielectric anisotropy abrupt change point.

[0011] Preferably, the energy dissipation monitoring is achieved through dielectric spectroscopy: An alternating electric field is applied in the direction perpendicular to the applied electric field; Real-time analysis of the frequency spectrum of the dielectric loss tangent tanδ; When the tanδ value at the characteristic frequency exceeds the set warning line, the field strength switching is triggered.

[0012] Preferably, the method further includes step 5: molecular chain orientation freezing. The resin treated with the electric field is placed in an alternating magnetic field, the intensity of which is adjusted according to the residual orientation degree. The crystal orientation factor is determined by X-ray diffraction, and the magnetic field strength is increased when the factor value is higher than the target range. The cooling rate decreases synchronously with the magnetic field frequency until room temperature is reached.

[0013] Preferably, the method for adjusting the magnetic field frequency is as follows: In the initial stage of cooling, a high-frequency magnetic field is used, with the frequency value being a multiple of the characteristic frequency of polymer chain segment motion. As the temperature decreases, the frequency decreases piecewise according to the rate of change of chain segment relaxation time predicted by the Arrhenius equation. The characteristic frequencies were determined at multiple temperature points using dynamic thermomechanical analysis.

[0014] Preferably, the injection rate of the capping agent is dynamically adjusted in the following manner: Establish a correlation model between the pressure change rate dP / dt and the end-group sealing efficiency: When dP / dt > 0, the injection rate is increased according to a parabolic function. When dP / dt < 0, maintain the current rate until the pressure rises again; The model was established based on the pressure-terminus concentration mapping relationship from previous experiments.

[0015] The beneficial effects of this invention are: 1. This invention employs a fatigue life-oriented monomer ratio design, mixing bisphenol A and fluorenylbisphenol monomers in a dynamically determined proportion. This precise ratio control ensures that the resin material exhibits superior fatigue performance under high-frequency amplitude loading while maintaining high tensile strength. In particular, by identifying the fatigue life inflection point and controlling the mixing ratio near this inflection point, early crack propagation is avoided, significantly improving the fatigue durability of the material.

[0016] 2. This invention achieves an ordered arrangement of rigid and flexible blocks in the molecular chain by precisely controlling the temperature, cooling rate, and end-capping agent injection rate during phase-sensing gradient polymerization. This structural design enables the resin to effectively prevent crack propagation under vibration loads, thus improving the material's crack resistance.

[0017] 3. This invention avoids the coexistence of high-temperature transesterification and pyrolysis reactions by precisely controlling amorphous confined solid-state thickening and graded electric field relaxation, thus reducing the generation of low molecular weight fragments. In particular, the dynamic temperature field control during polymerization ensures that the molecular chain structure of the resin remains stable at high temperatures, avoiding performance degradation caused by the broadening of molecular weight distribution.

[0018] 4. This invention ensures effective suppression of end-group degradation of the resin throughout the polymerization process by precisely controlling the end-capping agent injection rate and graded electric field relaxation. In particular, by dynamically adjusting the end-capping agent injection rate through a correlation model between pressure change rate and end-group sealing efficiency, the risk of excessively high end-group concentration is effectively reduced, thus avoiding stress corrosion cracking.

[0019] 5. This invention optimizes the molecular chain structure of the resin by freezing the molecular chain orientation and constructing a dynamic temperature field, and by using an alternating magnetic field and precise control of temperature changes. This ensures that the resin has good orientation and molecular chain structure during the production process, thereby reducing the generation of stress concentration sources and improving the stability and durability of the material under high load conditions. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in this invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0021] Figure 1 This is a flowchart of the steps of the method of the present invention; Figure 2This is a flowchart illustrating the steps of the method for observing the crystallization induction time in this invention. Figure 3 This is a flowchart illustrating the steps of the magnetic field frequency control method of the present invention. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. It should also be noted that, to make the embodiments more comprehensive, the following embodiments are the best and preferred embodiments, and those skilled in the art can use other alternative methods to implement some well-known technologies; moreover, the accompanying drawings are only for more specific description of the embodiments and are not intended to specifically limit the present invention.

[0023] Please see Figures 1-3 This invention provides a method for preparing high-strength polycarbonate resin. In step 1, the raw materials are selected by mixing bisphenol A and fluorene-based bisphenol monomers in a dynamically determined ratio, based on the inflection point of the fatigue life increase of the prepolymer under axial amplitude loading. The core of this step is to identify the critical point at which the fatigue life of the resin increases suddenly under load under specific fatigue conditions. In this way, it is ensured that the resin maintains high tensile strength and excellent fatigue resistance under long-term high-frequency amplitude loading. The optimized monomer ratio effectively improves the strength of the material (>70 MPa) and prevents the problem of decreased elongation at break caused by unreasonable monomer ratios in the prior art.

[0024] In step 2, during the polymerization process, the first stage involves heating to temperature T1, corresponding to the viscosity change rate threshold, and maintaining this temperature until the byproduct distillation rate reaches a safe critical value. The purpose of this stage is to effectively remove byproducts from the reaction during synthesis, ensuring the uniformity and stability of the resin molecular chains.

[0025] In the second stage, at temperature T2, variable-rate cooling is implemented based on real-time cloud point detection, and a sealing agent is injected. During this process, the injection rate of the sealing agent is linked to the pressure change rate of the reactor, ensuring effective sealing of the molecular chain end groups and avoiding the problem of uncontrolled end group degradation in existing technologies. This step effectively improves the resin's resistance to stress corrosion cracking and extends its service life.

[0026] In step 3, the polymer particles are treated with a dynamic temperature field in a moving bed. The range of the temperature field is dynamically set according to the difference between the resin's glass transition temperature Tg and crystallization initiation temperature Tc to ensure that the resin maintains a relatively ideal molecular structure throughout the processing. This treatment method reduces excessive molecular chain alignment by avoiding excessive crystallinity, thereby making the resin more flexible under stress and improving the material's resistance to crack propagation.

[0027] In step 4, under a high-voltage electric field, electric fields of different intensities are applied in two stages. In the first stage, the electric field intensity causes the molecular chains to reach the orientation saturation critical value. In the second stage, the electric field intensity is adjusted to reduce the birefringence back to a preset critical value. This process ensures the ordered orientation of the resin's molecular chains while avoiding the brittleness caused by over-orientation, thus enhancing the material's toughness and fatigue resistance.

[0028] Through the innovations in the aforementioned processes, particularly improvements in the ordered arrangement of molecular chains, end-group closure, and optimized fatigue life design, the technical bottlenecks of existing polycarbonate resins in terms of high strength, high-frequency load, and fatigue resistance have been overcome. These technological features enable the final resin to possess higher tensile strength (>70 MPa) and superior high-cycle fatigue resistance (>10 MPa) for applications such as aerospace drones. 7 It offers advantages such as longer service life (multiple cycles) and avoids molecular chain structure defects, low molecular weight fragments, and stress corrosion cracking problems found in existing technologies.

[0029] In one possible implementation, at least five different ratios of bisphenol A / fluorene bisphenol prepolymers are first prepared. These different ratio samples provide a variety of possible combinations for subsequent fatigue life testing. Depending on the ratio of each sample, it is used to simulate load conditions in real-world application scenarios.

[0030] Then, fatigue life tests were conducted on each sample under a load simulating the vibration spectrum of a drone wing. This load simulates the dynamic vibration conditions that may occur during actual flight, and can more accurately reflect the fatigue performance of the resin in high-load environments such as aircraft. Through this test, fatigue life data of the resin at each scale can be obtained.

[0031] Next, a fatigue life-ratio curve was plotted to analyze the correlation between the resin's fatigue life and the ratio of bisphenol A / fluorenylbisphenol. This curve allows observation of the resin's fatigue performance under different ratios, and the second derivative of the curve was calculated. By calculating the second derivative, the trend of the curve's change can be identified, and the inflection point of a sudden increase in fatigue life can be precisely determined.

[0032] Specifically, when the second derivative is zero and the signs on its left and right sides are different (i.e., the curve has undergone an extreme value change), it is marked as an inflection point. This inflection point represents the region of sudden increase in the material's fatigue life, meaning that the resin will exhibit the best fatigue resistance at this formulation.

[0033] Finally, the mixing ratio is controlled to remain within ± of the inflection point ratio. This deviation is determined by the reciprocal of the radius of curvature of the curve at the inflection point. This reciprocal of the radius of curvature reflects the sensitivity of the fatigue life curve near the inflection point, thus allowing for further fine-tuning of the ratio to ensure optimal resin performance under high load and high fatigue conditions.

[0034] By precisely identifying and optimizing the inflection point of fatigue life increase, the final resin formulation exhibits exceptional fatigue resistance in high-strength applications, making it particularly suitable for high-load, high-vibration environments such as drones. This method not only extends the resin's service life but also maintains the material's stability and reliability under high-intensity vibration conditions, solving the problem of fatigue failure that commonly occurs in traditional polycarbonate resins under high-frequency loads.

[0035] In one possible implementation, during the variable-rate cooling process, the first step is to determine whether the current temperature is above the cloud point based on the real-time temperature. The cloud point is a characteristic temperature at which a polymer solution begins to aggregate and form turbidity during cooling. Therefore, accurate determination of the cloud point is crucial for subsequent cooling strategies. The cloud point is determined by the point of abrupt change in scattered light intensity. When the intensity of scattered light changes significantly, it indicates that the solution has begun a phase transition and entered the turbid region; this temperature is the cloud point.

[0036] When the temperature is above the cloud point, a first cooling rate R1 is adopted. The value of R1 is adjusted based on the changing trend of the online laser scattering intensity. The laser scattering intensity is closely related to the degree of molecular aggregation in the polymerization system. When the scattering intensity increases to a set level, the step size of R1 is increased accordingly. The core of this process is to dynamically adjust the cooling rate by monitoring the molecular behavior in the solution in real time, ensuring that the polymer molecular chains aggregate in an orderly manner during the cooling process, thereby improving the structural stability and mechanical properties of the resin.

[0037] When the temperature drops below the cloud point, a second cooling rate R2 is applied. The value of R2 is then determined by the dielectric loss factor of the polymerization system. The dielectric loss factor reflects the energy absorption capacity of the polymerization system under an electric field. Within the dielectric loss peak temperature range, R2 is inversely proportional to the height of the loss peak. A higher loss peak indicates greater disorder in the molecular chains within the system; therefore, a slower cooling rate is needed to avoid excessive aggregation and uneven crystallization of the molecular chains, thereby ensuring the mechanical properties and fatigue resistance of the resin.

[0038] By implementing the above cooling strategies, the phase transition behavior and molecular structure of the resin during polymerization can be precisely controlled. The adjustment of the first cooling rate, R1, based on changes in laser scattering intensity, can promptly reflect the dynamic process of molecular aggregation in the solution, thereby effectively preventing excessively rapid polymer crystallization or the formation of inhomogeneous molecular structures. The adjustment of the second cooling rate, R2, through changes in the dielectric loss factor, ensures that the cooling rate is appropriately slowed when the polymer molecular chains are in an amorphous state, preventing premature or excessive molecular chain aggregation and effectively improving the resin's toughness, fatigue resistance, and long-term stability.

[0039] Therefore, the variable-rate cooling method provided by this invention has significant advantages in resin preparation. It can not only improve the mechanical properties of the material, but also enhance its durability in high-load, high-frequency vibration environments. It solves the problems of uneven cooling or inaccurate control in the prior art, thus providing strong technical support for the widespread application of high-strength polycarbonate resin.

[0040] In one possible implementation, the temperature at the inlet section is first set to Tg + ΔT1, where Tg is the glass transition temperature and ΔT1 is determined by observation using a hot-stage polarized light microscope. Specifically, when the heating rate is set to a fixed value, the ratio of crystallization induction time to solid-phase thickening time needs to be observed. Crystallization induction time refers to the time it takes for the polymer to change from a liquid to a solid state, while solid-phase thickening time is the process by which the resin changes from a fluid state to a more viscous state. By ensuring that the crystallization induction time exceeds twice the solid-phase thickening time and selecting an appropriate ΔT1 (temperature increment), premature crystallization of the resin upon entering the middle section can be effectively prevented, thereby ensuring the resin's fluidity and uniformity.

[0041] In the middle stage, the temperature is set to (Tg+Tc) / 2-ΔT2, where Tc is the crystallization temperature and ΔT2 is derived from the optimized molecular weight growth rate. Specifically, during resin polymerization, the molecular weight growth rate is monitored using online gel permeation chromatography. If a decreasing trend in the molecular weight growth rate is detected, it indicates that the polymerization reaction is no longer progressing smoothly, and ΔT2 needs to be adjusted appropriately. At this point, lowering ΔT2 and reducing the temperature can prevent over-polymerization and molecular chain entanglement, maintaining a suitable molecular weight and the final mechanical properties of the resin.

[0042] At the outlet section, a slow cooling strategy is employed to ensure that the cooling curve matches the polymer's free volume shrinkage rate. Free volume refers to the intermolecular spaces within the polymer, and changes in free volume directly affect the polymer's structure and mechanical properties. By precisely controlling the cooling rate, internal stress concentration during polymer crystallization caused by excessively rapid cooling can be avoided, thereby improving the overall strength and fatigue resistance of the resin.

[0043] By employing dynamic temperature control at different stages, not only is the molecular chain structure and crystallization state of the polycarbonate resin optimally controlled, but the overall performance of the resin is also effectively improved. Temperature control at the inlet stage prevents premature crystallization, temperature control in the middle stage optimizes molecular weight growth, and slow cooling at the outlet stage reduces internal stress and non-uniformity, thereby significantly improving the material's mechanical properties, heat resistance, and fatigue resistance.

[0044] In one possible implementation, the polymer sheet before thickening is first placed on a hot stage. During this process, the polymer sheet is under a nitrogen atmosphere to ensure that it is not affected by oxidation reactions. Next, heating is initiated by setting a constant heating rate; temperature control is a crucial aspect of this method. The choice of heating rate needs to balance the polymer crystallization process with temperature changes to ensure that the observed crystallization behavior is representative.

[0045] During the heating process, the formation of polymer crystal nuclei was observed in real time using a polarizing microscope. The polarizing microscope can clearly display the formation process of crystal nuclei in the polymer sheet using polarized light. During this process, crystal nuclei appear under the field of view of the polarizing microscope; these nuclei are a marker of the polymer's transformation from an amorphous state to a crystalline state. Through video stream analysis, the time of crystal nuclei appearance can be recorded, and the formation patterns at different temperatures can be compared.

[0046] To obtain more accurate and stable crystallization induction times, repeated tests at the target temperature are necessary until a stable induction time spectrum is obtained. Repeated experiments eliminate the influence of random factors on the crystallization induction time, ensuring the reliability and reproducibility of the results. Finally, by analyzing the crystallization induction time data at multiple temperatures, the crystallization behavior of the resin under different conditions can be determined, providing a basis for subsequent temperature control strategies.

[0047] This method for observing crystallization induction time, through precise control of the heating rate and nitrogen atmosphere environment combined with observation using a polarizing microscope, enables real-time tracking of the crystal nucleus formation process in polymer sheets, accurately obtaining the crystallization induction time. Stable induction time spectra were obtained through repeated tests, ensuring the accuracy and reliability of the data and providing a scientific basis for subsequent polymer temperature control optimization. This method not only improves the crystallization properties of polymers but also provides crucial data support for further resin performance optimization and molecular structure control, thereby enhancing the mechanical strength, thermal stability, and other key properties of the final resin, meeting the application requirements of high-strength polycarbonate resins in various industrial fields.

[0048] In one possible implementation, the electric field strength E1 in the first stage of field control is determined by online monitoring of the birefringence variation curve. The birefringence variation curve reflects changes in the molecular arrangement within the polymer. When the polymer's molecular structure changes during heating or temperature fluctuations, the birefringence also changes. By monitoring the birefringence variation in real time, it is observed whether the rate of change drops to a certain proportion of the initial value. This proportion indicates that a significant change has occurred in the polymer's molecular structure or crystallization state, thus determining the electric field strength E1 at that moment. The electric field strength E1 in this stage ensures that the resin is sufficiently subjected to the electric field in the initial stage, promoting the uniform arrangement of molecular chains and laying the foundation for subsequent polymerization and crystallization.

[0049] In the second stage, the electric field strength E2 is controlled by monitoring the energy dissipation during the relaxation process. The relaxation process refers to the loosening of the molecular chains, which is accompanied by energy dissipation. By monitoring energy dissipation in real time, the peak value of the dissipated power can be observed. When the dissipated power drops to a set safe threshold, the corresponding electric field strength is E2. Setting the electric field strength E2 in this stage ensures that once the polymer's molecular structure tends to stabilize, an excessively strong electric field is no longer applied, thus avoiding potential excessive electric field effects or polymer instability.

[0050] Determining the timing of field strength switching relies on identifying the dielectric anisotropy abrupt change point. Dielectric anisotropy refers to the difference in dielectric constant of a polymer in different directions. With the application of an electric field, the dielectric anisotropy of the polymer changes, and the abrupt change point is the moment when this change significantly reverses. By monitoring this abrupt change point, the timing of switching field strengths can be accurately determined, avoiding unnecessary negative impacts of the electric field on polymer properties.

[0051] This regulatory rule, through the scientific design and control of field strength changes, not only ensures the effective alignment of polymer molecular chains throughout the preparation process but also avoids structural instability caused by excessively strong electric fields. The first stage promotes initial crystallization and structural alignment of the polymer by controlling field strength E1; the second stage ensures the stability of the polymer structure and avoids excessive energy dissipation by optimizing E2; simultaneously, the application of dielectric anisotropy abrupt change points provides precise timing for field strength switching, further optimizing polymer performance. Through this dynamic field strength control, the resulting polycarbonate resin not only possesses excellent mechanical properties but also high thermal stability and fatigue resistance, meeting the requirements of high-strength applications.

[0052] In one possible implementation, firstly, during polymer processing, the applied electric field is directed vertically to ensure uniform application and comprehensive influence on the material's molecular structure. Simultaneously, an alternating electric field is applied to the polymer. The frequency of this alternating electric field needs precise control to analyze the material's dielectric loss characteristics at different frequencies.

[0053] Next, the frequency spectrum of the dielectric loss tangent (tanδ) of the material under an alternating electric field is analyzed in real time. This process involves a detailed frequency response analysis of the dielectric properties of the polymer material. The tanδ value reflects the energy dissipation of the polymer material under an electric field; a high tanδ value indicates greater energy loss, while a lower tanδ value indicates greater material stability. By analyzing the frequency spectrum, the loss characteristics of the polymer at different frequencies can be identified, especially certain specific "characteristic frequencies," which are the frequencies at which the material's energy dissipation changes significantly.

[0054] When the tanδ value at the characteristic frequency exceeds the preset warning line, it indicates that the polymer material has experienced significant energy loss. This may mean that the polymer's molecular arrangement or structure has become unstable, or that the polymer's reaction at that temperature has reached a critical state. At this point, the system will automatically trigger a field strength switch to adjust the applied electric field strength in a timely manner, preventing excessive energy dissipation from adversely affecting the polymer's performance.

[0055] By monitoring energy dissipation through dielectric spectroscopy, the energy loss of polymers at different stages can be precisely controlled. When the tanδ value exceeds a set warning line, an abnormal state of the material at that stage can be quickly identified, allowing for timely adjustment of the electric field strength and preventing performance degradation due to excessive energy dissipation. This method not only helps improve the precision of resin preparation but also ensures the stability of the polymer during the preparation process and its final high-strength properties. By precisely controlling the timing of field strength switching, the resulting polycarbonate resin will possess better mechanical properties, thermal stability, and long-term reliability.

[0056] In one possible implementation, the polycarbonate resin, which has already been treated with an electric field, is first placed in an alternating magnetic field. The alternating magnetic field affects the orientation of the resin molecular chains, causing them to align in a specific direction, thereby improving the resin's structural stability and strength. The strength of the magnetic field needs to be adjusted according to the resin's residual orientation, i.e., controlled based on the current orientation of the resin molecular chains. When the resin molecular chains already have a certain orientation, an appropriate magnetic field strength can further optimize their alignment, avoiding over-orientation that could lead to uneven material properties.

[0057] X-ray diffraction was used to measure the crystal orientation factor of the resin, which reflects the spatial arrangement of the resin molecular chains. A higher value indicates stronger orientation of the molecular chains. If the measured crystal orientation factor value exceeds a preset target range, it means that the resin molecular chain orientation has reached the desired effect. The magnetic field strength can then be appropriately increased to further optimize the molecular chain arrangement. In this way, the molecular structure of the resin is further refined, which helps to improve the mechanical properties of the material, such as strength and toughness.

[0058] Furthermore, during the orientation freezing process, the cooling rate and magnetic field frequency are reduced synchronously until room temperature. This synchronous reduction helps maintain the orientation of the resin molecular chains, ensuring that the molecular chains retain a reasonable degree of orientation during cooling and avoiding structural defects caused by excessively rapid cooling. By synchronously reducing the cooling rate and magnetic field frequency, the orientation structure of the resin can be stabilized during the cooling process, thereby further improving its overall performance.

[0059] This molecular chain orientation freezing step significantly improves the molecular arrangement of polycarbonate resin, enhancing its mechanical properties and thermal stability. By adjusting the intensity of the alternating magnetic field and precisely controlling the cooling rate, the resin molecular chains maintain their optimal orientation during cooling, thereby enhancing the resin's compressive strength, toughness, and fatigue resistance. X-ray diffraction measurements of the crystal orientation factor provide accurate molecular structure analysis, allowing for more scientific and effective adjustment of the magnetic field intensity. This ensures that the final resin possesses excellent properties, meeting the requirements of high-strength applications.

[0060] In one possible implementation, during the initial cooling phase, a high-frequency magnetic field is required to promote the directional alignment of resin molecular chains and ensure their effective response to the alternating magnetic field in the initial stage. The frequency of this high-frequency magnetic field should be set as a multiple of the characteristic frequency of polymer chain segment motion. The characteristic frequency of polymer chain segment motion is closely related to the dynamic behavior of the resin molecular chains; selecting this multiple ensures that the magnetic field matches the motion frequency of the resin molecular chains, thereby maximizing the effect of the magnetic field on molecular chain orientation. Using a high-frequency magnetic field during the initial cooling phase can effectively improve the mobility of the resin molecular chains, promote their alignment, and enhance the physical properties of the resin.

[0061] As the temperature decreases, the resin molecular chains gradually enter a cooling state, and their mobility decreases. Therefore, the frequency of the magnetic field needs to be adjusted according to the temperature change. This frequency adjustment follows the prediction of the Arrhenius equation, which describes the effect of temperature change on the relaxation time of the molecular chains (i.e., the relaxation behavior of chain segments). According to this equation, as the temperature decreases, the relaxation time of the chain segments gradually increases, and the movement of the molecular chains slows down. Therefore, the magnetic field frequency should be gradually reduced in a segmented manner to adapt to the changes in the relaxation time of the molecular chains. This adjustment ensures that the resin molecular chains maintain a good orientation structure during cooling, avoiding over-orientation or non-uniform orientation caused by excessively high magnetic field frequencies.

[0062] The characteristic frequencies were determined using dynamic thermomechanical analysis (DMA) at multiple temperature points. DMA technology can provide information on the dynamic mechanical behavior of resin materials at different temperatures, particularly the relaxation behavior of chain segments, thereby accurately determining the characteristic frequencies of the material. This method, by conducting real-time testing of the material's properties at different temperature points, can provide a scientific basis for the regulation of magnetic field frequencies, ensuring that changes in magnetic field frequencies match the molecular behavior of the resin.

[0063] Using a high-frequency magnetic field in the initial cooling stage can effectively promote the orderly arrangement of resin molecular chains, improving the resin's mechanical properties and thermal stability. As the temperature gradually decreases, gradually lowering the magnetic field frequency avoids excessive interference from high frequencies on the orientation of the resin molecular chains, ensuring that the resin molecular chains maintain their optimal alignment throughout the cooling process. Precise determination of characteristic frequencies through dynamic thermomechanical analysis allows for scientific guidance in adjusting the magnetic field frequency, making the magnetic field control process more precise and effective. This magnetic field frequency control method helps in the preparation of polycarbonate resins with higher strength and superior performance, meeting the requirements of high-strength applications.

[0064] In one possible implementation, firstly, a correlation model between the pressure change rate (dP / dt) and end-group sealing efficiency was established through preliminary experimental studies. The pressure change rate reflects the rate of pressure change in the reaction system, while the end-group sealing efficiency is related to factors such as the reaction rate of the end-capping agent and reaction conditions. Based on the previous mapping relationship between pressure and end-group concentration, the precise relationship between the pressure change rate and the end-group sealing efficiency can be calculated. This model provides a theoretical basis and operational guidance for dynamically adjusting the injection rate of the end-capping agent.

[0065] During the reaction, if the rate of pressure change (dP / dt) is greater than zero, meaning the pressure of the reaction system is increasing, this usually indicates that the reaction is underway and there is a sufficient supply of reactants. In this case, the injection rate of the capping agent can be increased using a parabolic function. The parabolic function is used to precisely control the injection rate based on the dynamic changes in pressure, keeping it matched to the reaction progress and avoiding incomplete or uneven reactions caused by injecting the capping agent too quickly or too slowly.

[0066] When the rate of change of pressure (dP / dt) is less than zero, it means that the pressure in the reaction system has decreased, which may indicate that the reaction process has been inhibited or that some kind of instability has occurred. In this case, the injection rate of the capping agent should remain constant until the pressure recovers. This strategy helps prevent overreaction or instability caused by an excessively rapid injection rate, while also providing sufficient time for pressure recovery to avoid interfering with the smooth progress of the reaction process.

[0067] This dynamic adjustment strategy allows for precise control of the end-capping agent injection rate based on real-time reaction conditions, ensuring the end-group sealing reaction proceeds under optimal conditions and thus improving resin performance. The core of this process lies in using the pressure change rate (dP / dt) to determine the reaction state and adjusting the injection rate as needed to ensure high efficiency and stability.

[0068] This dynamic adjustment method for the end-capping agent injection rate achieves precise control of the reaction process by establishing an accurate correlation model, avoiding the inefficiency and performance instability caused by excessively fast or slow injection rates. The use of a parabolic function provides a flexible adjustment method for optimizing the injection rate, ensuring the reaction remains optimal at different stages and maximizing end-group sealing efficiency. Furthermore, real-time monitoring and adjustment of pressure changes allows for timely responses to changes during the reaction, guaranteeing both high reaction efficiency and the high strength properties of the polycarbonate resin. This method significantly improves the overall performance of polycarbonate resin, meeting the demands of high-strength applications.

[0069] The following examples will illustrate this in detail: This invention relates to a method for improving the strength and performance of polycarbonate resin by dynamically adjusting the injection rate of the end-capping agent, particularly by utilizing the correlation between the rate of change of pressure (dP / dt) and the end-group sealing efficiency to achieve precise control of the injection rate, thereby optimizing the final performance of the resin.

[0070] This experiment was conducted on conventional polycarbonate resin synthesis equipment, the main equipment of which included: Reactor: 10L capacity, equipped with real-time temperature and pressure monitoring devices.

[0071] Injection pump: Used to precisely control the injection rate of the capping agent.

[0072] Gas pressure control system: used to regulate the pressure inside the reactor.

[0073] Cooling system: Maintains the required temperature range during the reaction process.

[0074] The reaction conditions are set as follows: Temperature: 210°C.

[0075] Reaction time: 3 hours.

[0076] End-capping agent: The end-capping agent used is a mixture of dichloromethane (DCM) and a certain isocyanate compound, with a concentration of 20%.

[0077] Catalyst: Triethanolamine, concentration 0.1%.

[0078] In previous experiments, the relationship between end-face sealing efficiency and pressure change rate (dP / dt) was measured under different pressure change rates. Through fitting the experimental data, the following relationship was derived: ; in, For end-base sealing efficiency, The rate of change of pressure, This is a constant obtained by fitting experimental data, with the following specific values: ; This model shows that when the rate of pressure change is positive, the end-group sealing efficiency is proportional to the square of the rate of pressure change, indicating that the more intense the end-group sealing process, the higher the end-group sealing efficiency.

[0079] Based on the aforementioned correlation model, the capping agent injection rate ( The adjustments will follow these strategies: When the rate of change of pressure At this point, the reaction is proceeding normally, and the injection rate increases parabolically to ensure rapid completion of the reaction. The specific injection rate formula is: ; in, These values ​​are the optimal constants obtained through previous experiments.

[0080] When the rate of change of pressure At this point, the reaction may be inhibited or unstable, and the injection rate remains constant until the pressure recovers. Specifically, the maintained injection rate is the initial injection rate. Until the pressure returns to its previous level.

[0081] At the beginning of the reaction, the initial pressure in the reactor is 1.0 MPa. As the capping agent is injected, the reaction produces gas, causing the pressure to gradually increase. During this process, the system calculates the pressure change rate in real time. The injection rate of the end-capping agent is dynamically adjusted according to the formula.

[0082] Initially, the pressure increases rapidly. According to the formula, the injection rate increases parabolically to 1.4 mL / min. ).

[0083] When the reaction reaches the middle stage, the rate of pressure change becomes negative. The injection rate was maintained at 1.0 mL / min until the pressure rose back to 1.2 MPa.

[0084] Throughout the reaction process, the system continuously optimizes the injection rate of the capping agent based on real-time pressure changes.

[0085] To verify the effectiveness of the present invention, two sets of comparative experiments were conducted: Control group: A fixed injection rate of 1.0 mL / min was used during the reaction, without any dynamic adjustment strategy.

[0086] Experimental group: The injection rate was dynamically adjusted based on the pressure change rate according to the method of the present invention.

[0087] The final properties of the polycarbonate resin were compared between the two experimental groups, and the results are as follows: Control group: The resin had a tensile strength of 60 MPa and an impact toughness of 10 kJ / m. 2 .

[0088] Experimental group: The tensile strength of the resin was 75 MPa, and the impact toughness was 14 kJ / m. 2 .

[0089] Therefore, by dynamically adjusting the injection rate of the end-capping agent, the strength and toughness of the resin are significantly improved, verifying the effectiveness of the method of the present invention.

[0090] According to the model's predictions, when the pressure change rate is large, the injection rate of the end-capping agent increases, ensuring efficient reaction and thus improving end-group sealing efficiency. Experimental data show that the experimental group using dynamic injection rate achieved a significantly higher end-group sealing efficiency, exceeding 90%, while the control group achieved approximately 80%.

[0091] By adjusting the injection rate in real time, the reaction can be optimized according to the actual needs, avoiding incomplete or unstable reactions caused by injecting the end-capping agent too quickly or too slowly, thereby improving the overall performance of the resin.

[0092] In this embodiment, a correlation model between pressure change rate and end-group sealing efficiency was employed to precisely control the injection rate of the end-capping agent, resulting in a significant improvement in the performance of polycarbonate resin. Compared with traditional methods, the method of this invention can dynamically adjust the injection rate at different reaction stages, maximizing reaction efficiency and resin performance. The application of this technology provides a new optimization path for the industrial production of polycarbonate resin, with good practical prospects and economic benefits.

[0093] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0094] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength polycarbonate resin, characterized in that, Perform the following steps in sequence: Step 1: Fatigue life-oriented monomer ratio design: Bisphenol A and fluorenylbisphenol monomers are mixed in a dynamically determined ratio, which is identified by the inflection point of the prepolymer fatigue life increase under axial amplitude load. Step 2: Phase-aware gradient aggregation: The first stage involves heating to the temperature T1 corresponding to the viscosity change rate threshold and maintaining it until the by-product distillation rate reaches a safe critical value. The second stage implements variable-rate cooling based on real-time cloud point detection, and injects the end-capping agent at the critical temperature T2 of the terminal hydroxyl concentration. The injection rate is linked to the rate of change of pressure in the reactor. Step 3: Amorphous confined solid-state thickening: The polymer particles are treated in a moving bed dynamic temperature field, and the temperature field range is dynamically set according to the difference between the glass transition temperature Tg and the crystallization initiation temperature Tc. Step 4: Electric field graded relaxation: Apply the electric field strength in two stages in a high-voltage electric field. The electric field strength in the first stage is taken as the critical value of molecular chain orientation saturation, and the electric field strength in the second stage is taken as the critical value of birefringence shrinking to a preset ratio.

2. The method for preparing a high-strength polycarbonate resin according to claim 1, characterized in that, The identification of the inflection point of sudden increase in fatigue life includes: Prepare bisphenol A / fluorenyl bisphenol prepolymers in at least five different ratios; Fatigue life was tested under simulated loads based on the vibration spectrum of a UAV wing. Plot the life-proportion curve and calculate the second derivative. Take the point where the derivative is zero and the left and right sides have opposite signs as the inflection point. The mixing ratio is controlled within the range of the inflection point ratio ± deviation, whereby the deviation is determined by the reciprocal of the radius of curvature of the curve at the inflection point.

3. The method for preparing a high-strength polycarbonate resin according to claim 1, characterized in that, The variable rate cooling method described in step 2 is implemented as follows: When the real-time temperature is higher than the cloud point, the first cooling rate R1 is adopted, and its value is adjusted according to the trend of online laser scattering intensity change: for every set increase in scattering intensity, R1 increases by the corresponding step size. When the real-time temperature is below the cloud point, a second cooling rate R2 is adopted, the value of which is determined by the dielectric loss factor of the polymerization system: within the dielectric loss peak temperature range, R2 is inversely proportional to the loss peak height. The turbidity point is determined by the point of abrupt change in the intensity of scattered light.

4. The method for preparing a high-strength polycarbonate resin according to claim 1, characterized in that, Step 3 involves constructing the dynamic temperature field, which includes: The inlet temperature was set to Tg+ΔT1, and ΔT1 was determined by observation using a hot-stage polarizing microscope: when the heating rate was set, the temperature increment was taken to be more than twice the solid phase thickening time of the crystallization induction time. The intermediate temperature is maintained at (Tg+Tc) / 2-ΔT2, and ΔT2 is optimized by the molecular weight growth rate: when the molecular weight growth rate is detected to decrease by online gel permeation chromatography, ΔT2 is adjusted down proportionally. The outlet section is cooled gradually, and the cooling curve matches the polymer free volume shrinkage rate.

5. The method for preparing a high-strength polycarbonate resin according to claim 4, characterized in that, The method for observing the crystallization induction time is as follows: The polymer sheet before thickening was placed on a hot table and heated at a constant rate under a nitrogen atmosphere. The occurrence time of crystal nuclei was analyzed using a polarizing microscope video stream. Repeat the test at the target temperature until a stable induction time spectrum is obtained.

6. The method for preparing a high-strength polycarbonate resin according to claim 1, characterized in that, The field strength adjustment rule mentioned in step 4 is as follows: The first stage field strength E1 is determined by the online birefringence change curve, and is the field strength corresponding to the rate of change dropping to the first proportion of the initial value. The second-stage field strength E2 is determined by monitoring the energy dissipation during the relaxation process, and is taken as the field strength at which the peak dissipation power is reduced to a safe threshold. The timing of field strength switching is determined based on the dielectric anisotropy abrupt change point.

7. The method for preparing a high-strength polycarbonate resin according to claim 6, characterized in that, The energy dissipation monitoring is achieved through dielectric spectroscopy: An alternating electric field is applied in the direction perpendicular to the applied electric field; Real-time analysis of the frequency spectrum of the dielectric loss tangent tanδ; When the tanδ value at the characteristic frequency exceeds the set warning line, the field strength switching is triggered.

8. The method for preparing a high-strength polycarbonate resin according to claim 1, characterized in that, It also includes step 5: molecular chain orientation freezing: The resin treated with the electric field is placed in an alternating magnetic field, the intensity of which is adjusted according to the residual orientation degree. The crystal orientation factor is determined by X-ray diffraction, and the magnetic field strength is increased when the factor value is higher than the target range. The cooling rate decreases synchronously with the magnetic field frequency until room temperature is reached.

9. The method for preparing a high-strength polycarbonate resin according to claim 8, characterized in that, The method for adjusting the frequency of the magnetic field is as follows: In the initial stage of cooling, a high-frequency magnetic field is used, with the frequency value being a multiple of the characteristic frequency of polymer chain segment motion. As the temperature decreases, the frequency decreases piecewise according to the rate of change of chain segment relaxation time predicted by the Arrhenius equation. The characteristic frequencies were determined at multiple temperature points using dynamic thermomechanical analysis.

10. The method for preparing a high-strength polycarbonate resin according to claim 1, characterized in that, The injection rate of the capping agent is dynamically adjusted in the following manner: Establish a correlation model between the pressure change rate dP / dt and the end-group sealing efficiency: When dP / dt > 0, the injection rate is increased according to a parabolic function. When dP / dt < 0, maintain the current rate until the pressure rises again; The model was established based on the pressure-terminus concentration mapping relationship from previous experiments.

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