High-frequency low-dielectric-constant modified polyphenyl ether and preparation process thereof

Abstract

The invention relates to the technical field of polyether terminal chemical modification, and discloses high-frequency low-dielectric constant modified polyphenyl ether and a preparation process thereof, and the high-frequency low-dielectric constant modified polyphenyl ether is generated by carrying out nucleophilic substitution reaction on hydroxyl-terminated polyphenyl ether, 3, 5-di-tert-butyl salicyloyl chloride and an organic base catalyst in an aromatic hydrocarbon solvent; the method comprises the following steps of: introducing an asymmetric steric hindrance structure at the tail end of a molecular chain, physically locking a polarity center to turn polarization by utilizing a space exclusion volume, and performing self-limiting on the steric hindrance by adopting a mode of dropwise adding a modifier at a constant speed and monitoring a change slope of a hydroxyl conversion rate in combination with an infrared spectrum so as to trigger steric hindrance self-limiting termination. A local hydrophobic field generated at the moment of precipitation is utilized to induce generation of a nanoscale closed-pore cavity, dielectric loss eigen-frequency insensitivity is achieved, and the product has excellent dielectric stability and thermal mechanical rigidity and effectively blocks water molecule permeation.

Description

Technical Field

[0001] This invention relates to a high-frequency, low-dielectric-constant modified polyphenylene ether and its preparation process, belonging to the field of polyether end-chemical modification technology. Background Technology

[0002] Currently, polyphenylene oxide (PPE) is used as the core resin base material for high-frequency communication copper-clad laminates. It is often modified by end-capping to reduce the influence of polar groups on dielectric constant and dielectric loss in humid and hot environments.

[0003] In high-frequency communication applications, conventional modification paths conflict in maintaining dielectric stability and thermomechanical strength. Introducing long-chain flexible groups increases the spacing between molecular chain segments and intensifies thermal motion, lowering the glass transition temperature of the material. This leads to a decrease in the dimensional stability and heat resistance of multilayer printed circuit boards during processing. Modification with fluorinated reagents increases production costs and complicates process requirements. In addition to the limitations of physical modification, precise quantitative control of the chemical reaction process is a major challenge. For example, Chinese invention patent CN115073285A discloses a method for synthesizing 3,5-diiodosalicylic acid chloride, which focuses on the yield and purity of pharmaceutical intermediates. It does not consider the demands of the high-frequency electronics industry for dipole polarization and end steric hindrance effects. Due to the lack of macromolecular chain end topological reshaping, it is impossible to shield the microscopic oscillation of the polar center through asymmetric steric hindrance. It is difficult to achieve precise self-limitation of the reaction endpoint using kinetic feedback, resulting in high dielectric loss of the modified product under ultra-high frequency electric fields and difficulty in maintaining the thermomechanical rigidity of the resin.

[0004] Therefore, the technical problem to be solved by this invention is how to reshape the topological structure of the macromolecule end to achieve dipole space locking and optimize free volume while maintaining the rigidity of the polyphenylene ether backbone. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A high-frequency, low-dielectric-constant modified polyphenylene ether is prepared by reacting raw materials comprising the following parts by weight:

[0006] 100 parts of hydroxyl-terminated polyphenylene ether, the weight-average molecular weight of the hydroxyl-terminated polyphenylene ether is 3000 to 15000 g / mol, and the hydroxyl value of the hydroxyl-terminated polyphenylene ether is 50 to 54 mg KOH / g.

[0007] 12 to 25 parts of modifier, wherein the modifier is 3,5-di-tert-butylsalicylic acid chloride;

[0008] 5 to 15 parts of organic base catalyst;

[0009] The solvent is at least one of toluene or xylene;

[0010] The modified polyphenylene ether has 3,5-di-tert-butylsalicylic acid groups introduced at the ends of its molecular chains;

[0011] Modified polyphenylene ether was prepared by the following reaction procedure: A modifier was added dropwise at a rate of 0.5 to 1.5 mL / min to a solution of hydroxyl-terminated polyphenylene ether at 65 to 75 °C. The area change of the hydroxyl absorption peak at 3400 to 3600 cm⁻¹ was monitored in real time using infrared spectroscopy to calculate the rate of change of the hydroxyl absorption peak area over time. ,when The reaction is determined to have entered the sterically hindered self-limiting stage and the reaction is terminated.

[0012] The modified polyphenylene ether has an end-capping rate of 95.5% to 97.5% and a molecular weight distribution index (PDI) of less than 1.45.

[0013] The 3,5-di-tert-butylsalicylic acid group utilizes the asymmetric steric repulsion of the tert-butyl groups at the 3 and 5 positions of the benzene ring to restrict the dipole orientation of the ester group center at the end of the molecular chain under an alternating electric field. During the precipitation of the modified polyphenylene ether molecular chain, the local hydrophobic field induces the construction of an air-containing nanoscale closed-pore structure between the molecular chain segments, thereby reducing the intrinsic dielectric loss of the modified polyphenylene ether.

[0014] Preferably, the modified polyphenylene ether has a weight-average molecular weight of 3500 to 12000 g / mol; the mass fraction of 3,5-di-tert-butylsalicylic acid is 3.5% to 7.5% of the total mass of the modified polyphenylene ether; the organic base catalyst is at least one of triethylamine, pyridine, or diisopropylethylamine; the dry dielectric constant of the modified polyphenylene ether at 10 GHz is 2.41 to 2.43, and the dielectric constant fluctuation after boiling water treatment for 24 h is less than 0.02; the dielectric loss Df of the modified polyphenylene ether at 28 GHz is less than 0.0020.

[0015] Preferably, the two tert-butyl groups in the 3,5-di-tert-butylsalicylic acid group are asymmetrically distributed at the 3 and 5 positions of the benzene ring. The resulting mass center bias constructs a physical anchoring field to limit the phase lag of the ester dipoles formed at the ends of the modified polyphenylene ether molecular chains under an ultra-high frequency electric field.

[0016] Preferably, the hydroxyl-terminated polyphenylene ether is pretreated by the following steps: the hydroxyl-terminated polyphenylene ether is added to a solvent and stirred at a speed of 300 to 500 rpm until the system becomes transparent, so that the polyphenylene ether molecular chains are stretched and the terminal hydroxyl active sites are exposed.

[0017] Preferably, the preparation process includes the following precipitation procedure: cooling the reaction solution after the reaction is terminated to 25 to 30°C, and injecting it into anhydrous methanol at a flow rate of 45 to 55 mL / min, with a volume of 3 to 4 times that of the reaction solution; during the precipitation process, the local hydrophobic field of 3,5-di-tert-butylsalicylic acid oxy group generates a repulsive force, inducing the molecular chain segments to spontaneously construct free volume cavities.

[0018] Preferably, in the precipitation process, the flow rate of injected anhydrous methanol is controlled. This reduces the microporosity of modified polyphenylene ether. The following quantitative rules must be met: ,in, The proportionality coefficient is related to the grafting rate of 3,5-di-tert-butylsalicylic acid at the end of the hydroxyl-terminated polyphenylene ether. This is a constant term related to the initial weight-average molecular weight of the hydroxyl-terminated polyphenylene ether.

[0019] Preferably, after filtration and washing, the modified polyphenylene ether is vacuum dried for 12 hours at 80 to 90°C and a pressure of less than 100 Pa to remove residual solvent and hydrogen chloride byproduct generated in the reaction.

[0020] Preferably, the rigid hindered structure in the 3,5-di-tert-butylsalicylic acid group restricts the thermal motion of the main chain segments of the modified polyphenylene ether, thereby making the glass transition temperature of the modified polyphenylene ether higher than 218°C and its axial thermal expansion coefficient lower than 45 ppm / °C.

[0021] Preferably, the end-capping rate of the modified polyphenylene ether is 96.2% to 96.5%; the dielectric loss Df of the modified polyphenylene ether at a frequency of 28 GHz tends to 0 with frequency; the terminal groups of the modified polyphenylene ether product block the formation of a continuous hydrogen bond permeation network of water molecules inside the material by constructing a strong hydrophobic field, which is reflected in the water absorption rate of less than 0.03% under 24h immersion conditions.

[0022] A high-frequency, low-dielectric-constant modified polyphenylene ether and its preparation process are disclosed, comprising the following steps: adding 3,5-di-tert-butylsalicylic acid chloride dropwise to a solution of hydroxyl-terminated polyphenylene ether at a rate of 0.5 mL / min to 1.5 mL / min, and monitoring the area change of the hydroxyl absorption peak at 3400 to 3600 cm⁻¹ in real time using infrared spectroscopy, and calculating the rate of change of the hydroxyl absorption peak area over time. ,when The reaction was terminated to obtain a reaction solution; the reaction solution was injected into anhydrous methanol, and the repulsive force generated by the local hydrophobic field of 3,5-di-tert-butylsalicylic acid oxy group was used to induce the spontaneous construction of nanoscale free volume cavities by polyphenylene ether molecular chain segments.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. In high-frequency, low-dielectric-constant modified polyphenylene ether, an asymmetric steric hindrance anchoring structure is introduced at the end of the polyphenylene ether macromolecular chain, so that the ester group center generated by the reaction is deeply buried in the branched rigid hydrocarbon surrounding ring; this structure uses the mass center bias and spatial repulsion volume to limit the micro-oscillation amplitude of the dipole under the alternating electric field, blocking the reversal polarization path, so that the dielectric loss of the material under high-frequency conditions exhibits intrinsic frequency insensitivity.

[0025] 2. The local steric shielding effect generated by the asymmetric branched alkyl groups in the modifier causes kinetic decay as the terminal hydroxyl modification reaction approaches its endpoint with the nonlinear increase in crowding around the active site, triggering a self-limiting reaction mechanism. This ensures the stability of the molecular weight distribution of the modified product and avoids excessive reaction leading to molecular chain degradation or byproduct residue. The asymmetric steric anchoring structure constructs a non-uniformly distributed free volume between molecular chains, utilizing the low dielectric properties of air to counteract the electronic polarization of chain segments. The gear effect between rigid groups restricts the thermal motion of the polyphenylene ether backbone, increasing the glass transition temperature while reducing the dielectric constant, thus resolving the contradiction between improved dielectric properties and decreased thermomechanical rigidity in conventional modification.

[0026] 3. The strong hydrophobic field at the end groups of the modified product and the hydrophobic gradient induction during the precipitation process cause the molecular chains to spontaneously construct a closed-pore topology with a high-density hydrophobic community during precipitation. This blocks the formation of a continuous hydrogen bond permeation network within the water molecule material, ensuring stable dielectric parameters under humid and hot conditions and improving the reliability of electronic substrates in extreme environments. Precise control of the kinetic state and precipitation morphology during chemical modification allows for the reshaping of the microscopic physical properties of polyphenylene ether using inexpensive basic chemical intermediates, demonstrating process universality and engineering application value. This addresses the need for intrinsically low-loss resins in high-frequency circuit substrates without increasing production equipment costs. Attached Figure Description

[0027] Figure 1 This is a flow chart of the preparation process of modified polyphenylene ether based on the kinetic self-limiting mechanism of the present invention;

[0028] Figure 2 This is a correlation distribution diagram of the end-capping rate and microporosity of the product under different molecular weight raw materials according to the present invention;

[0029] Figure 3 This is a block diagram illustrating the principle of the intelligent preparation system for modified polyphenylene ether with integrated spectral feedback control according to the present invention. Detailed Implementation

[0030] The present invention will be further described in detail below with reference to specific embodiments. The specific embodiments described herein are intended to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0031] This invention provides a high-frequency, low-dielectric-constant modified polyphenylene ether and its preparation process. By introducing anchoring groups with asymmetric steric hindrance structures at the ends of the hydroxyl-terminated polyphenylene ether molecular chains, the polar centers are shielded by physical spatial repulsion. Combined with a controlled precipitation process, a nanoscale closed-pore structure is constructed within the product, achieving low dielectric loss and high thermal stability at 28 GHz. The modified polyphenylene ether is prepared using 100 parts by weight of hydroxyl-terminated polyphenylene ether as the reaction base. The weight-average molecular weight of the hydroxyl-terminated polyphenylene ether is... The concentration of the reactant solution is between 3000 g / mol and 15000 g / mol, and the hydroxyl value ranges from 50 mg KOH / g to 54 mg KOH / g. To eliminate the influence of different batches of raw material molecular weight on the molecular chain extension state and to establish a quantitative benchmark for the solvent treatment stage, the mass concentration of the reactant solution is... Based on weight-average molecular weight Perform pre-conditioning procedures, mass concentration with weight average molecular weight Satisfy linear rules ,in, This represents the mass percentage of hydroxyl-terminated polyphenylene ether in an aromatic hydrocarbon solvent. This refers to the weight-average molecular weight of hydroxyl-terminated polyphenylene ether, expressed in g / mol; according to this procedure, when the weight-average molecular weight... The mass concentration was set at 12000 g / mol. The concentration was 18%, with toluene or xylene used as the reaction solvent. The terminal hydroxyl polyphenylene ether was added to the reaction solvent and stirred continuously at 300 rpm to 500 rpm until the system became transparent. This concentration threshold was used to compensate for the entanglement resistance caused by the increased molecular chain length, ensuring that the effective collision probability between the modifier and the active hydroxyl sites at the microscopic level was consistent. 12 to 25 parts by weight of 3,5-di-tert-butylsalicylic acid chloride was used as the modifier. For different batches of terminal hydroxyl polyphenylene ether, to ensure that the end-capping rate of 3,5-di-tert-butylsalicylic acid oxygen at the molecular chain end was consistently within the range of 95.5% to 97.5%, a feeding calibration procedure targeting the hydroxyl concentration of the raw material was initiated, and the hydroxyl value of the raw material was measured. Then, the amount of organic base catalyst required per 100 parts by weight of raw material Follow the relation ; This refers to the parts by weight of organic base catalysts; The value represents the hydroxyl group of the hydroxyl-terminated polyphenylene ether, expressed in mgKOH / g. The molar mass of the organic base catalyst is given. The excess reaction coefficient is 1.1 to 1.3. According to the procedure, the amount of organic base catalyst is set to be in the range of 5 parts by weight to 15 parts by weight. The organic base catalyst is one or more of triethylamine, pyridine or diisopropylethylamine.

[0032] Under a constant temperature environment of 65℃ to 75℃, the modifier was added dropwise to the hydroxyl-terminated polyphenylene ether solution at a constant rate of 0.5 mL / min to 1.5 mL / min using a metering pump. The addition process was monitored by infrared spectroscopy at 3400 cm⁻¹. Up to 3600cm Calculate the rate of change of the area of ​​the characteristic absorption peak of the hydroxyl group over time. An infrared spectral feedback closed-loop control architecture was constructed, and an absorbance reference sequence was set within the detection window. The original discrete data is processed using a smoothing filter, and the location is determined by the second derivative method. Peak center, real-time calculation of integral area With sampling step size rate of change If within three consecutive sampling periods An interrupt instruction is executed when the fluctuation deviation is below a threshold. The judgment criterion is based on the weight-average molecular weight. Corresponding to the shielding kinetic curve of the terminal active sites, the reaction solution is forced into an isothermal aging stage to correct for the spurious increase in local concentration caused by solvent evaporation, ensuring that the end-capping rate achieves intrinsic loss convergence under extremely high frequency conditions. When the absolute value of the rate of change is detected... When the value is less than 0.005, it is determined that the nonlinear steric hindrance triggers a self-limiting kinetic effect due to end-group space crowding. At this point, the reaction is terminated, and a modified polyphenylene ether solution is obtained. The end-capping rate of the modified polyphenylene ether is in the range of 95.5% to 97.5%, and the weight-average molecular weight is [not specified]. The distribution index (PDI) is less than 1.45. The modified polyphenylene oxide (PPE) has a 3,5-di-tert-butylsalicylic acid group introduced at the end of its molecular chain. The two tert-butyl groups at the 3 and 5 positions of the benzene ring are asymmetrically distributed. This creates a physical anchoring field through the resulting center-of-mass bias, limiting the phase lag of the ester dipoles formed at the end of the modified PPE molecular chain under an ultra-high frequency electric field. This blocks the reorientation polarization path, reducing the dielectric loss of the material at 28 GHz. Less than 0.0020.

[0033] After cooling the reaction solution to 25°C to 30°C, proceed with the reaction at a flow rate of 45 mL / min to 55 mL / min. When injected into anhydrous methanol at a volume of 3 to 4 times that of the reaction solution, the local hydrophobic field of 3,5-di-tert-butylsalicylic acid oxychloride generates a repulsive force during precipitation, inducing the spontaneous construction of air-containing nanoscale closed-pore structures within the polyphenylene ether molecular chains. These closed-pore structures reduce the intrinsic dielectric loss of the modified polyphenylene ether and decrease its microporosity. The following quantitative rules must be met: In the formula, The microporosity of the modified polyphenylene ether; The flow rate of anhydrous methanol injected; This is a proportionality coefficient, the value of which is determined by the grafting rate of 3,5-di-tert-butylsalicylic acid at the end of the hydroxyl-terminated polyphenylene ether. This is a constant term, the value of which is determined by the initial weight-average molecular weight of the terminal hydroxyl polyphenylene ether. It was determined that an integrated multi-dimensional fluid dynamics compensation procedure was used to monitor the dynamic viscosity of the reaction liquid in real time. With temperature Parameters, based on the porosity prediction model Dynamically calculate the optimal injection flow rate The PID controller is invoked to adjust the output frequency of the metering pump, and the flow rate compensation step size is set. Related to the grafting rate of 3,5-di-tert-butylsalicylic acid. If the system back pressure exceeds the calibrated safety threshold Initiating bypass shunt logic, this control strategy is based on different The batch chain segment entanglement resistance experimental data were used to synchronously adjust the cooling water flow rate of the nanoforming module, stabilize the hydrophobic field to repel energy level differences, and lock the average pore size of the closed-cell structure. for This method addresses the challenge of uneven microscopic topological distribution in large-scale preparation. The precipitated product, after filtration and washing with anhydrous methanol, is dried for 12 hours in a vacuum environment at 80°C to 90°C and a pressure below 100 Pa to remove residual solvent and hydrogen chloride byproducts generated during the reaction. The dried modified polyphenylene ether exhibits a dielectric constant of 2.41 to 2.43 at 10 GHz, with a dielectric constant fluctuation of less than 0.02 after 24 hours of boiling water treatment. The glass transition temperature of the product is lower than that of the polyphenylene ether because the rigid hindered structure in the 3,5-di-tert-butylsalicylic acid group restricts the thermal motion of the polyphenylene ether backbone. Above 218℃, the axial thermal expansion coefficient is less than 45ppm / ℃, and the water absorption rate of modified polyphenylene ether under 24h impregnation conditions is less than 0.03%.

[0034] Example 1: In the production process of 28GHz high-frequency communication copper-clad laminates, the polar groups at the ends of the modified polyphenylene ether resin experience dielectric loss due to phase lag in polarization under ultra-high frequency electric fields. Furthermore, conventional end-capping groups cannot block the hydrogen bond penetration pathway of moisture molecules in humid and hot environments, leading to a drift in the dielectric constant and limiting the material's stability in high-frequency applications. To address the challenges posed by polar loss, 100 parts by weight of weight-average molecular weight... Hydroxyl-terminated polyphenylene ether with a concentration of 12000 g / mol and a hydroxyl value of 52 mg KOH / g was dissolved in toluene. At 70°C and a rotation speed of 400 rpm, 18 parts by weight of 3,5-di-tert-butylsalicylic acid chloride as a modifier were added dropwise to the hydroxyl-terminated polyphenylene ether solution at a rate of 1.0 mL / min. The addition was monitored in real-time using infrared spectroscopy at 3500 cm⁻¹. The evolution of the area of ​​the characteristic absorption peak of hydroxyl groups was studied, and the rate of change of the area of ​​the characteristic absorption peak of hydroxyl groups over time was calculated. When the absolute value of the rate of change is detected When the value is less than 0.005, the asymmetric steric hindrance structure is determined to trigger the kinetic self-limiting mechanism and terminate the reaction, thereby introducing 3,5-di-tert-butylsalicylic acid group into the molecular chain end of the obtained modified polyphenylene ether.

[0035] After cooling the above reaction solution to 25°C, the solution was then flowed at a rate of 50 mL / min. Precipitation was induced by injecting four times the volume of anhydrous methanol. The asymmetric hydrophobic field formed by the tert-butyl groups at the 3 and 5 positions of the benzene ring in the 3,5-di-tert-butylsalicylic acid group generated local repulsive forces, inducing the polyphenylene ether molecular chains to arrange themselves in a loosely packed manner at the moment of precipitation. This spontaneously generated a nanoscale closed-pore structure within the resin matrix, modifying the microporosity of the polyphenylene ether. Satisfy the following formula: ,in, The micropores of modified polyphenylene ether, The flow rate of anhydrous methanol to be injected, This is a proportionality coefficient, the value of which is determined by the grafting rate of 3,5-di-tert-butylsalicylic acid at the end of the hydroxyl-terminated polyphenylene ether. This is a constant term, the value of which is determined by the initial weight-average molecular weight of the terminal hydroxyl polyphenylene ether. The dielectric loss of the modified polyphenylene ether after vacuum drying at 85℃ was determined at 28 GHz. Its glass transition temperature is 0.0018. The temperature was 221℃, and the water absorption rate after boiling water treatment for 24 hours was 0.02%, which shows that the modified polyphenylene ether maintains dielectric stability and thermomechanical rigidity due to the synergistic effect of the asymmetric steric structure physically locking the polar center to turn the polarization path and the nanoscale closed-pore structure induced by the hydrophobic field reducing the polarization intensity of the material.

[0036] Example 2: In the experimental scenario verifying the dielectric response and damp-heat stability at 28 GHz, a sealed reactor with zoned temperature control was constructed, and the temperature fluctuation range was controlled within... Within 0.5℃, the reaction process is monitored in situ using an infrared spectrometer equipped with an attenuating total internal reflection component, and the wavenumber resolution of the infrared spectrometer is not less than 2 cm⁻¹. To simulate thermodynamic disturbances in an industrial environment, random thermal noise with an amplitude of 2% of the set temperature was actively introduced during the experiment, and a metering pump with a flow accuracy class of 0.5 was used to control the dripping rate of the modifier. Core parameter: Drop acceleration rate The underlying logic is to balance the instantaneous concentration of acyl chloride groups with the diffusion rate of the system, when the dropping acceleration rate... Within the range of 0.5 mL / min to 1.5 mL / min, 3,5-di-tert-butylsalicylic acid chloride molecules can effectively migrate to the molecular chain ends before the gelation effect occurs; if the rate exceeds 1.5 mL / min, local heat of reaction leads to uncontrolled side reactions of the side chains; the preparation of both the experimental and control groups is based on weight-average molecular weight. The initial hydroxyl-terminated polyphenylene ether was 12000 g / mol with a hydroxyl value of 52 mg KOH / g. The composition ratio and performance test results of each sample group are shown in Table 1.

[0037] Table 1: Component ratios and performance test results for each sample group

[0038]

[0039] By observing the data in Table 1, it can be found that sample group 1 of the present invention operates at a frequency of 28 GHz. The value was lower than that of control group 1, which was capped with benzoyl chloride. This is because the asymmetric distribution of tert-butyl groups in the 3,5-di-tert-butylsalicylic acid group creates a physical anchoring field, which restricts the orientation polarization behavior of the terminal ester dipoles under a high-frequency electric field. This was achieved by comparing sample group 1 of this invention with the precipitation flow rate. In control group 2 (120 mL / min), it was found that when When the molecular chain increases, its kinetic energy is high at the moment of precipitation, resulting in insufficient local hydrophobic repulsion from the 3,5-di-tert-butylsalicylic acid group to induce the formation of a nanoscale closed-pore structure, thus reducing the material's micropore density. The decrease is reflected in the dielectric constant. The water absorption rate of control group 3 increased from 0.021% to 0.123% due to the incomplete capping of terminal hydroxyl groups caused by the residual polar hydroxyl groups at ultra-high frequency, and the hydrogen bonding effect caused the water absorption rate to increase from 0.021% to 0.123%. In control group 4, the excessive side chain structure produced a plasticizing effect after the amount of modifier exceeded 25 parts by weight, leading to a decrease in the glass transition temperature. The temperature dropped to 204.5℃; experimental data confirmed that the modifier content was between 12 and 25 parts by weight and the precipitation flow rate was [not specified]. The system operates within the optimal window for dielectric properties and thermal stability at a flow rate of 45 mL / min to 55 mL / min.

[0040] Example 3: This example combines Figures 1 to 3 This document describes a high-frequency, low-dielectric-constant modified polyphenylene ether and its preparation process. Figure 1 As shown, the preparation process of this high-frequency, low-dielectric-constant modified polyphenylene ether begins with the raw material pretreatment stage. After mixing the terminal hydroxyl polyphenylene ether, aromatic hydrocarbon solvent, and organic base catalyst, the process proceeds to the modifier addition step, where 3,5-di-tert-butylsalicylic acid chloride is added at a rate of 0.5 to 1.5 mL / min. A nucleophilic substitution reaction occurs under a constant temperature environment of 65 to 75 °C. During the reaction, the infrared spectroscopy monitoring module continuously monitors the temperature from 3400 to 3600 nm. The area of ​​the hydroxyl absorption peak is measured and the rate of change k is calculated. The data is transmitted in real time to the kinetic self-limitation judgment step. If the rate of change... If the value is less than 0.005, it is considered a positive result and enters the steric hindrance self-limitation termination stage. At this point, the asymmetric steric hindrance structure triggers a kinetic self-limiting effect. Otherwise, the reaction continues. After the reaction is terminated, the system is injected into the precipitant methanol, entering the structural remodeling and precipitation stage. A nanoscale closed-pore structure is constructed by inducing the local hydrophobic field. Finally, after filtration, washing, and drying, a sealing rate between 95.5% and 97.5% is obtained. High-frequency, low-dielectric-constant modified polyphenylene ether with a dielectric constant of <0.0020.

[0041] like Figure 2 As shown in the biaxial bar chart, the horizontal axis indicates the three weight-average molecular weight specifications of hydroxyl-terminated polyphenylene ether, namely 3000 g / mol, 8000 g / mol, and 15000 g / mol. The left vertical axis of the chart corresponds to the end-capping rate (%) represented by the grid-textured bars, and the right vertical axis corresponds to the microporosity represented by the dot-textured bars. The figure shows, side by side, the end-capping ratio and microporosity of the modified polyphenylene ethers prepared under the three different molecular weight conditions mentioned above. The specific quantitative distribution of the values; such as Figure 3 As shown, the system includes a centrally located intelligent isothermal reaction core as a steric hindrance self-limiting generation zone. To its left is a precision feeding module for performing uniform dripping and injection of the modifier. Above the system is a process control center responsible for spectral analysis and endpoint determination. This center receives hydroxyl peak data from the reaction core through a dotted path and feeds back termination / lock commands to the precision feeding module and the reaction core. The reaction liquid transfer path is connected to the nanoforming module on the right, which performs hydrophobic induced precipitation. After a curing step, the final output is a low-dielectric finished powder / particle.

[0042] Example 4: In the mass production of copper-clad laminates for high-gain array antennas for 5G millimeter-wave base stations, the dielectric constant of modified polyphenylene ether... Consistency is limited by microporosity The fluctuations are due to the varying initial weight-average molecular weights of different batches of hydroxyl-terminated polyphenylene ether. The presence of discreteness causes the volume fraction of nanoscale closed-pore structures formed during the precipitation process to deviate from the set value, resulting in a dielectric constant deviation exceeding 0.05 between different production batches and hindering precise control of the antenna phase. To solve this consistency problem, a parameter calibration procedure is performed before initiating the modification reaction, selecting a weight-average molecular weight... Hydroxyl-terminated polyphenylene ether samples of 3000 g / mol, 8000 g / mol, and 15000 g / mol were prepared into a 18% (w / w) reaction solution in toluene solvent. The reaction temperature was controlled at 70 °C, and 3,5-di-tert-butylsalicylic acid chloride was added at a dropping rate of 1.0 mL / min. Infrared spectroscopy was used with a sampling period of 30 s. Collected from 3500cm hydroxyl absorbance data The original absorbance sequence was denoised using a five-point cubic smoothing algorithm, and the following calculations were performed. rate of change at time as follows: ,in, The rate of change of absorbance over time; This is the absorbance value after filtering at the current sampling time; This represents the absorbance value at the previous sampling time. The sampling period is measured in seconds; when a sample is detected... When the concentration remained stable below 0.005 for three consecutive sampling periods, the reaction was determined to have reached the steric hindrance self-limiting equilibrium point. At this point, the end-capping rate of each group of products was measured. The experimentally determined... When the molecular chain length is increased from 3000 g / mol to 15000 g / mol, the equilibrium end-capping rate decreases from 97.4% to 95.6%. This trend indicates that the increase in molecular chain length increases the probability of the terminal groups wrapping into the system, thereby enhancing the steric shielding effect generated by the 3,5-di-tert-butylsalicylic acid group.

[0043] The modified reaction solution was flowed at a rate of 50 mL / min. The product was injected into anhydrous methanol, and the microporosity of the resulting product was measured. The calibration results show the parameters in the calibration formula, specifically the proportional coefficient. It increases linearly with the increase of the end-capping ratio, and its value is 0.042 when the end-capping ratio is 96.5%. (Constant term) Compared with the initial weight-average molecular weight Follow the mapping rules as follows: ,in, This is the constant term in the porosity formula; This represents the weight-average molecular weight of hydroxyl-terminated polyphenylene ether, expressed in g / mol. Based on the above calibration results, when using weight-average molecular weight... When the raw material is 12000 g / mol, the calculation is as follows: It is 0.267, at the injection flow rate Predict microporosity under the condition of 50 mL / min The value was 0.431. The calibrated parameters were input into the production control system. The resulting modified polyphenylene ether had a high microporosity. Stable at 0.431 Its dielectric constant at 10 GHz is within the range of 0.005. The dielectric constant is stable at 2.42, and the inter-batch dielectric drift is reduced to below 0.008. Due to the precise matching between the asymmetric steric structure and the precipitation flow rate, the nanoscale closed-pore structure inside the modified polyphenylene ether achieves uniform spatial distribution, solving the problem of signal transmission phase deviation caused by dielectric performance fluctuations in large-scale production.

[0044] Example 5: In the continuous production of modified polyphenylene ether for high-frequency copper-clad laminates above 28GHz, residual organic base catalyst and reaction byproduct hydrogen chloride lead to dielectric loss in the material. The temperature rises under humid and hot conditions, and the residual solvent causes uneven thickness and internal stress concentration during the copper clad laminate pressing process; to eliminate the interference of impurity ions on polarization characteristics, a steric hindrance self-limiting modification reaction is completed and the absolute value of the rate of change is detected. Once the conductivity is less than 0.005, the washing and neutralization procedure is initiated. Deionized water at a volume ratio of 1.0:5.0 is added to the reaction solution, and the mixture is stirred at 450 rpm for 15 minutes. After standing and separating the layers, the aqueous phase is removed. This operation is repeated until the conductivity of the aqueous phase reaches the specified value. Below 10 S / cm; conductivity Follow the rules ,in, The conductivity of the current aqueous phase, in units of S / cm; The initial conductivity during the first wash; Number of washes; To determine the cleaning efficiency constant, a multi-stage programmed temperature-increasing vacuum drying procedure was executed after washing to remove residual toluene solvent. The washed modified polyphenylene ether solution was introduced into a vacuum tower, with the top pressure set at 1500 Pa and the temperature at 85 °C to remove volatiles. The resin paste with a solid content higher than 95% was transferred to a vacuum oven, where it was heated to 115 °C at a rate of 2 °C / min and held at that temperature for 6 hours under a pressure lower than 100 Pa. The rigid framework formed by the tert-butyl groups at the 3 and 5 positions of the benzene ring in the 3,5-di-tert-butylsalicylic acid group maintained the micro-closed-pore topology during solvent escape. The modified polyphenylene ether product after treatment had a chloride ion mass fraction of less than 5 ppm and a toluene residue of less than 0.01%. The dielectric loss was measured at 28 GHz. The value is 0.0018 and the batch-to-batch fluctuation is less than 0.0001.

[0045] Example 6: When performing a pressing process on a multilayer board and requiring the interlayer thickness deviation to be less than... Under certain operating conditions, the average pore size of the nanoscale closed-pore structure inside the modified polyphenylene ether is... Deviations from the preset value will cause discontinuities in the characteristic impedance. To establish a deterministic control path for the physical structure parameters, a linear cooling procedure is initiated after the modification reaction is terminated, controlling the initial temperature of the cooling water in the reactor jacket to be [value missing]. And the traffic remains at The reaction solution was transferred from according to cooling rate Down to And maintain a constant temperature Average aperture With cooling rate Satisfying quantitative relationship ,in, The average pore size of the nanoscale closed-pore structure is expressed in units of 100 nm. ; The cooling rate is expressed in units of 1. ; The correction factor is determined by the grafting rate of 3,5-di-tert-butylsalicylic acid at the end of the hydroxyl-terminated polyphenylene ether. The basic pore size constant is determined by the initial weight-average molecular weight of the terminal hydroxyl polyphenylene ether. Sure.

[0046] In an environment where the humidity fluctuates from 45% to 65% at the production site, the hydrophobic shielding effect generated by the asymmetric steric hindrance field of the tert-butyl group in 3,5-di-tert-butylsalicylic acid ether inhibits water penetration. The average pore size of the nanoscale closed-pore structure in the modified polyphenylene ether obtained through a controlled cooling process is... In to Within the range, and the standard deviation of the pore size distribution is lower than The thickness deviation between the substrate layers of the copper-clad laminate after pressing and molding is less than And the characteristic impedance fluctuation range is within Within.

[0047] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-frequency, low-dielectric-constant modified polyphenylene ether, characterized in that, It is prepared by reacting the following raw materials in parts by weight: 100 parts of hydroxyl-terminated polyphenylene ether, the weight-average molecular weight of the hydroxyl-terminated polyphenylene ether is 3000 to 15000 g / mol, and the hydroxyl value of the hydroxyl-terminated polyphenylene ether is 50 to 54 mg KOH / g. 12 to 25 parts of modifier, wherein the modifier is 3,5-di-tert-butylsalicylic acid chloride; 5 to 15 parts of organic base catalyst; The solvent is at least one of toluene or xylene; The modified polyphenylene ether has 3,5-di-tert-butylsalicylic acid groups introduced at the ends of its molecular chains; Modified polyphenylene ether was prepared by the following reaction procedure: A modifier was added dropwise at a rate of 0.5 to 1.5 mL / min to a solution of hydroxyl-terminated polyphenylene ether at 65 to 75 °C. The area change of the hydroxyl absorption peak at 3400 to 3600 cm⁻¹ was monitored in real time using infrared spectroscopy to calculate the rate of change of the hydroxyl absorption peak area over time. ,when The reaction is determined to have entered the sterically hindered self-limiting stage and the reaction is terminated. The modified polyphenylene ether has an end-capping rate of 95.5% to 97.5% and a molecular weight distribution index (PDI) of less than 1.

45. The 3,5-di-tert-butylsalicylic acid group utilizes the asymmetric steric repulsion of the tert-butyl groups at the 3 and 5 positions of the benzene ring to restrict the dipole orientation of the ester group center at the end of the molecular chain under an alternating electric field. During the precipitation of the modified polyphenylene ether molecular chain, the local hydrophobic field induces the construction of an air-containing nanoscale closed-pore structure between the molecular chain segments, thereby reducing the intrinsic dielectric loss of the modified polyphenylene ether.

2. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1, characterized in that, The modified polyphenylene ether has a weight-average molecular weight of 3500 to 12000 g / mol; the mass fraction of 3,5-di-tert-butylsalicylic acid is 3.5% to 7.5% of the total mass of the modified polyphenylene ether; the organic base catalyst is at least one of triethylamine, pyridine, or diisopropylethylamine; the dry dielectric constant of the modified polyphenylene ether at 10 GHz is 2.41 to 2.43, and the dielectric constant fluctuation after boiling water treatment for 24 h is less than 0.02; the dielectric loss Df of the modified polyphenylene ether at 28 GHz is less than 0.0020.

3. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1, characterized in that, The two tert-butyl groups in 3,5-di-tert-butylsalicyloyloxy are asymmetrically distributed at the 3 and 5 positions of the benzene ring. By creating a mass center bias, a physical anchoring field is constructed to limit the phase lag of the ester dipoles formed at the ends of the modified polyphenylene ether molecular chains under an ultra-high frequency electric field.

4. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1, characterized in that, Hydroxyl-terminated polyphenylene ether is pretreated by the following steps: adding the hydroxyl-terminated polyphenylene ether to a solvent and stirring at 300 to 500 rpm until the system becomes transparent, so that the polyphenylene ether molecular chains can be stretched out and the terminal hydroxyl active sites can be exposed.

5. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1, characterized in that, The preparation process includes the following precipitation procedure: the reaction solution after the reaction is terminated is cooled to 25 to 30°C and injected into anhydrous methanol at a flow rate of 45 to 55 mL / min, with a volume of 3 to 4 times that of the reaction solution; during the precipitation process, the local hydrophobic field of 3,5-di-tert-butylsalicylic acid oxy group generates a repulsive force, inducing the molecular chain segments to spontaneously construct free volume cavities.

6. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 5, characterized in that, In the precipitation process, the flow rate of injected anhydrous methanol is controlled. This reduces the microporosity of modified polyphenylene ether. The following quantitative rules must be met: ,in, The proportionality coefficient is related to the grafting rate of 3,5-di-tert-butylsalicylic acid at the end of the hydroxyl-terminated polyphenylene ether. This is a constant term related to the initial weight-average molecular weight of the hydroxyl-terminated polyphenylene ether.

7. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1, characterized in that, After filtration and washing, the modified polyphenylene ether is vacuum dried for 12 hours at 80 to 90°C and a pressure of less than 100 Pa to remove residual solvent and hydrogen chloride byproduct generated in the reaction.

8. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1, characterized in that, The rigid hindered structure in 3,5-di-tert-butylsalicylic acid group restricts the thermal motion of the main chain segments of the modified polyphenylene ether, resulting in a glass transition temperature higher than 218°C and an axial thermal expansion coefficient lower than 45 ppm / °C for the modified polyphenylene ether.

9. The high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1, characterized in that, The end-capping rate of the modified polyphenylene ether is 96.2% to 96.5%; the dielectric loss Df of the modified polyphenylene ether at 28 GHz frequency tends to 0 with frequency; the terminal groups of the modified polyphenylene ether product block the formation of a continuous hydrogen bond permeation network of water molecules inside the material by constructing a strong hydrophobic field, which is reflected in the water absorption rate of less than 0.03% under 24h immersion conditions.

10. A high-frequency, low-dielectric-constant modified polyphenylene ether and its preparation process, characterized in that, The preparation of the high-frequency, low-dielectric-constant modified polyphenylene ether according to claim 1 comprises the following steps: uniformly adding 3,5-di-tert-butylsalicylic acid chloride dropwise to a solution of hydroxyl-terminated polyphenylene ether at a rate of 0.5 mL / min to 1.5 mL / min, and monitoring the area change of the hydroxyl absorption peak at 3400 to 3600 cm⁻¹ in real time using infrared spectroscopy, and calculating the rate of change of the area of ​​the hydroxyl absorption peak with time. ,when The reaction was terminated to obtain a reaction solution; the reaction solution was injected into anhydrous methanol, and the repulsive force generated by the local hydrophobic field of 3,5-di-tert-butylsalicylic acid oxy group was used to induce the polyphenylene ether molecular chain segments to construct nanoscale free volume cavities.

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