Low-ionic precipitation type halogen-free flame retardant for electronic products and preparation method thereof

Abstract

The application belongs to the technical field of flame retardant materials, and particularly relates to a low-ion-precipitation type halogen-free flame retardant for electronic products and a preparation method thereof. The method uses a phosphorus-nitrogen type halogen-free flame retardant as raw material, first generates active sites on the surface of the flame retardant powder through low-temperature plasma irradiation, then generates a silane coupling agent containing a crown ether group in situ in anhydrous ethanol by pre-reaction of the silane coupling agent and a hydroxymethyl crown ether, adds deionized water to start hydrolysis and polycondensation, forms a crown ether functionalized polysiloxane crosslinking layer in situ on the surface of the particles, and finally drives the free sodium and potassium ions in the particles to diffuse outward and be selectively complexed, captured and fixed by the crown ether layer under the condition of ultrasonic-assisted warm water immersion washing. The application solves the problem of the deterioration of the electrical properties of a polymer insulating material in a humid heat environment caused by residual ion impurities of the flame retardant.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant materials technology, specifically relating to a low-ion precipitation type halogen-free flame retardant for electronic products and its preparation method. Background Technology

[0002] As electronic devices continue to evolve towards miniaturization, high-density packaging, and high-voltage, high-current operation, the industry is placing increasingly stringent demands on the electrical reliability of polymer insulating materials. While halogen-free flame retardants, represented by phosphorus and nitrogen compounds, are widely used in the electronics and electrical engineering fields, a prominent problem has emerged in practical applications: water-soluble conductive impurities such as sodium, potassium, and chloride ions inevitably remain during the production and synthesis of these flame retardants. When engineering plastic parts containing these flame retardants are exposed to high-temperature and high-humidity environments for extended periods, these ionic impurities gradually dissolve from the flame retardant and migrate directionally to the material surface and metal contact areas under the combined influence of concentration gradients and electric fields. This forms ionic conductive channels within the matrix and on the surface, leading to a continuous decrease in the material's volume resistivity and surface resistivity. When these ions migrate to metal terminals or circuit wiring areas, they can also trigger electrochemical corrosion, which in severe cases can lead to insulation breakdown and abnormal signal transmission.

[0003] Regarding the harm of ionic impurities to the reliability of electronic materials, patent CN200880013496.7 points out that epoxy resin raw materials used in sealing materials for electronic components often contain ionic impurities such as halide ions and sodium ions, which can adversely affect electronic components. Patent CN202310234246.5 further states that impurities such as sodium ions, potassium ions, and chloride ions from toughening agents in epoxy adhesives can easily cause ion migration and dendritic crystallization, and points out that adding cation exchangers or anion exchangers alone cannot eliminate this problem. Both of the above documents use the method of adding ion exchangers or ion traps to the resin formulation to capture ionic impurities that have entered the system, which is a passive defense strategy and cannot eliminate ionic impurities carried by the flame retardant raw materials themselves from the source.

[0004] To address the issue of flame retardant precipitation in humid and hot environments, existing research primarily focuses on improving compatibility and constructing surface coatings. Patent CN201811440424.X points out that the significant precipitation of flame retardants during humid and hot aging not only affects product appearance but can also, in severe cases, reduce the electrical properties of materials. This paper addresses this by compounding specific types of ammonium polyphosphate with polyol phosphate esters and supplementing them with hydrolysis-resistant stabilizers to improve the compatibility between the flame retardant and the resin matrix, thereby inhibiting precipitation. However, such methods only address the physical problem of flame retardant particles migrating from the plastic matrix and do not address the removal of existing ionic impurities in the flame retardant raw materials. Patent CN104098775B describes the problem of halogen-free intumescent flame retardants easily migrating and precipitating under high temperature and high humidity environments, resulting in low surface treatment efficiency and susceptibility to damage. This paper instead employs an intermolecular cross-linking technique, indirectly confirming the inherent defects of surface coatings, such as easy damage and limited protective effect under processing and application conditions.

[0005] In summary, existing technologies either focus on adding scavenging agents to the resin formulation to passively capture dissolved ions, or on inhibiting the macroscopic physical migration of flame retardants through surface modification and formulation optimization. Neither approach addresses the fundamental chemical problem of ionic impurities inherent in the flame retardant raw materials themselves. Therefore, developing a halogen-free flame retardant capable of removing ionic impurities at the source and controlling the content of conductive ions to extremely low levels is urgently needed to ensure the electrical safety and lifespan of high-end electronic products under complex operating conditions. Summary of the Invention

[0006] The purpose of this invention is to provide a low-ion leaching halogen-free flame retardant for electronic products and its preparation method. It aims to solve the problem that existing halogen-free flame retardants cause a decrease in the resistance and corrosion failure of polymer insulating materials due to the dissolution and migration of residual ionic impurities in humid, hot and electric field environments. By deeply purifying the flame retardant, the content of conductive ionic impurities is controlled at an extremely low level, thereby meeting the stringent requirements of precision electronic components for high insulation and long-term reliability.

[0007] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products, comprising the following steps: (1) Spread phosphorus-nitrogen halogen-free flame retardant powder on the sample stage of a low-temperature plasma treatment device, and irradiate the surface of the flame retardant powder under vacuum of 10~50Pa and inert atmosphere to obtain a surface-activated flame retardant. (2) Dissolve the silane coupling agent with 2-hydroxymethyl-15-crown-5 and hydroxymethyl-18-crown-6 in anhydrous ethanol, add triethylamine, and perform a pre-reaction. Then add deionized water to the reaction solution, stir, and prepare a coupling agent deposition solution. Immerse the surface-activated flame retardant obtained in step (1) into the coupling agent deposition solution and stir the reaction under an inert atmosphere. After the reaction is completed, filter, wash with anhydrous ethanol, and then cure under an inert atmosphere and at a temperature of 90~120℃ to obtain a flame retardant intermediate with a surface-bonded crown ether structure. (3) Add the flame retardant intermediate obtained in step (2) to deionized water, stir and soak under ultrasonic conditions; after soaking, filter, rinse the filter cake with deionized water, and dry to obtain the low ion precipitation type halogen-free flame retardant.

[0008] Further, the phosphorus-nitrogen-based halogen-free flame retardant in step (1) is selected from any one or a mixture of several of aluminum hypophosphite, aluminum diethylphosphite, melamine polyphosphate, and melamine cyanurate.

[0009] Further, in step (1), the phosphorus-nitrogen-based halogen-free flame retardant powder is spread to a thickness of 3-8 mm on the sample stage of the low-temperature plasma treatment equipment; the irradiation treatment time is 120-300 seconds.

[0010] Further, in step (2), the silane coupling agent is 3-glycidoxypropyltrimethoxysilane (KH-560); the mass ratio of the total mass of the silane coupling agent, 2-hydroxymethyl-15-crown-5, and hydroxymethyl-18-crown-6 to anhydrous ethanol is 1:20~35; the mass of the deionized water is 5%~15% of the total mass of the silane coupling agent, 2-hydroxymethyl-15-crown-5, and hydroxymethyl-18-crown-6; and the amount of triethylamine added is 1%~5% of the total mass of the silane coupling agent, 2-hydroxymethyl-15-crown-5, and hydroxymethyl-18-crown-6.

[0011] Further, in step (2), the mass ratio of hydroxymethyl-18-crown-6 to 2-hydroxymethyl-15-crown-5 is 1:0.5~2.0; the amount of silane coupling agent is 20%~50% of the total mass of 2-hydroxymethyl-15-crown-5 and hydroxymethyl-18-crown-6; and the total amount of silane coupling agent, 2-hydroxymethyl-15-crown-5 and hydroxymethyl-18-crown-6 is 3%~9% of the mass of flame retardant.

[0012] Furthermore, in step (2), the temperature of the pre-reaction is 40~60℃ and the time of the pre-reaction is 30~60 minutes.

[0013] Furthermore, the temperature of the stirring reaction in step (2) is 70~85℃, and the stirring reaction time is 90~120 minutes.

[0014] Further, in step (3), the mass ratio of the flame retardant intermediate to deionized water is 1:8~15.

[0015] Furthermore, in step (3), the conductivity of the immersion solution is measured every 15 minutes during the immersion process. When the change in two consecutive measurements is not greater than 5% of the last measurement, the immersion is terminated.

[0016] The second aspect of this invention provides a low-ion precipitation halogen-free flame retardant for electronic products, which is obtained by the above-mentioned preparation method of a low-ion precipitation halogen-free flame retardant for electronic products.

[0017] This invention constructs a cross-linked layer with ion-selective trapping function around the flame retardant particles. This layer intercepts and firmly complexes and locks outward-diffusing impurity ions from the particle interior, preventing the ions from freely migrating and thus achieving confined deactivation. Specifically, low-temperature plasma treatment generates free radical sites and active hydroxyl groups on the surface of the flame retardant powder, providing anchor points for the subsequent chemical bonding of the coupling agent and preventing the cross-linked layer from detaching during subsequent processing due to mere physical adhesion. A silane coupling agent is dissolved in anhydrous ethanol with 2-hydroxymethyl-15-crown-5 and hydroxymethyl-18-crown-6, and pre-reacted under triethylamine catalysis. This allows the epoxy groups of the silane coupling agent to undergo ring-opening grafting with the hydroxymethyl groups on the crown ether molecule, generating a silane coupling agent containing crown ether groups in situ. Subsequently, a measured amount of deionized water is added to controllably initiate a hydrolysis-condensation reaction, immersing the surface-activated flame retardant in the reaction. This causes the coupling agent to undergo directional condensation on the particle surface, forming a crown ether-functionalized polysiloxane cross-linked layer. Two crown ethers, hydroxymethyl-18-crown-6 and 2-hydroxymethyl-15-crown-5, were combined to utilize the high degree of matching between their cavity sizes and those of potassium and sodium ions, respectively. This allowed for the simultaneous arrangement of two types of trapping sites within the cross-linked layer, achieving synergistic capture of the two main conductive ionic impurities. Subsequently, under ultrasonic-assisted warm water immersion conditions, the ultrasonic cavitation effect and concentration gradient jointly drove the accelerated diffusion of free ions from within the particles. As the diffused ions crossed the particle surface, they were selectively complexed by the crown ether cavities through ion-dipole interactions, forming stable complexes that were locked within the cross-linked network. Simultaneously, the ion diffusion equilibrium was monitored online by changes in the conductivity of the immersion solution. Immersion was terminated when the change in two consecutive measurements did not exceed 5%. The sodium and potassium ions, bound and fixed by the crown ethers, lost their free migration ability and could not participate in conductive or electrochemical corrosion under subsequent humid heat and electric field conditions. Furthermore, the siloxane cross-linked network provided hydrophobic barrier properties, inhibiting the penetration of external moisture into the particles. This effectively solved the problem of residual flame retardant ionic impurities leading to the degradation of the electrical properties of polymeric insulating materials.

[0018] The crown ether functionalized polysiloxane crosslinking layer used in this invention is covalently anchored to the surface of flame retardant particles. The amount added is only a few percent of the flame retardant's mass, and it is an inert nano-thin layer that does not participate in or interfere with the char formation and expansion flame retardant process of the flame retardant in the condensed phase. Simultaneously, the surface organic treatment improves the compatibility and dispersion uniformity of the flame retardant powder and the resin matrix, which is beneficial for fully realizing the flame retardant effect. Sodium and potassium ions trapped by crown ether cavitation form stable host-guest complexes and are firmly locked in the covalent crosslinking network. Under subsequent damp heat and electric field service conditions, they cannot escape and participate in conductive or electrochemical corrosion, thus achieving permanent confined deactivation of impurity ions.

[0019] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: This invention fundamentally changes the traditional approach of purifying flame retardants by relying on elution and separation. Through low-temperature plasma activation, in-situ grafting and anchoring of crown ethers, and ultrasonic-assisted immersion and capture, a covalently cross-linked layer with ion-selective capture function is constructed on the surface of the flame retardant particles. This layer permanently deactivates free sodium and potassium ions within the particles by in-situ complexing and locking them in crown ether cavities, rather than transferring them to an external solvent. The preparation conditions are mild and controllable, resulting in a low-ion-emission halogen-free flame retardant with extremely low residual ionic impurities. When added to engineering plastics, it maintains excellent insulation reliability under humid heat and electric field conditions, effectively solving the industry problem of insulation degradation and electrochemical corrosion of electronic components caused by residual ionic impurities in flame retardants. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Unless otherwise specified, all raw materials used in the embodiments are commercially available products. The following sources are illustrative examples.

[0022] Aluminum diethylphosphinic acid and melamine cyanurate were purchased from Jinan Hongtu New Materials Co., Ltd.; melamine polyphosphate was purchased from Shandong Yinglang Chemical Co., Ltd.; 2-hydroxymethyl-15-crown-5 (CAS: 75507-25-4) and hydroxymethyl-18-crown-6 (CAS: 70069-04-4) were purchased from TCI (Shanghai) Chemical Industry Development Co., Ltd.

[0023] Example 1 This embodiment provides a low-ion precipitation type halogen-free flame retardant for electronic products, the preparation method of which includes the following steps: (1) Take 200g of aluminum diethylphosphinate powder and spread it evenly on the sample stage of the low-temperature plasma treatment equipment with a spreading thickness of 5mm. Under the conditions of vacuum degree 30Pa and nitrogen atmosphere, generate low-temperature plasma with radio frequency power of 100W and frequency of 13.56MHz to irradiate the surface of the flame retardant powder for 180 seconds to obtain the surface-activated flame retardant.

[0024] (2) Dissolve 3g of KH-560, 5g of 2-hydroxymethyl-15-crown-5, and 5g of hydroxymethyl-18-crown-6 in 325g of anhydrous ethanol, add 0.4g of triethylamine, and stir for 45 minutes under nitrogen atmosphere protection and temperature of 55℃ to allow the epoxy group of KH-560 to undergo a ring-opening grafting reaction with the hydroxymethyl group on the crown ether molecule; then add 1.3g of deionized water to the reaction solution, stir evenly, and prepare a coupling agent deposition solution; immerse the flame retardant obtained in step (1) in the coupling agent deposition solution, and stir for 100 minutes under nitrogen atmosphere protection and temperature of 80℃; after the reaction is completed, filter, wash the filter cake with anhydrous ethanol, and then cure for 60 minutes under nitrogen atmosphere and temperature of 105℃ to obtain a flame retardant intermediate with a surface-bonded crown ether structure.

[0025] (3) Add the flame retardant intermediate obtained in step (2) to 2000g of deionized water, stir and soak for 60 minutes at a temperature of 65℃, an ultrasonic frequency of 28kHz and an ultrasonic power of 250W. During the soaking process, take a sample every 15 minutes to measure the conductivity of the soaking solution. When the change in the two measured values ​​at the 45th minute and the 60th minute is 3.2%, which is less than 5%, stop the soaking. After the soaking is completed, filter, rinse the filter cake with deionized water, and vacuum dry at 85℃ for 8 hours to obtain the low ion precipitation type halogen-free flame retardant.

[0026] Example 2 This embodiment provides a low-ion precipitation type halogen-free flame retardant for electronic products, the preparation method of which includes the following steps: (1) Take 200g of melamine polyphosphate powder and spread it evenly on the sample stage of the low-temperature plasma treatment equipment with a thickness of 4mm. Under the conditions of vacuum degree 20Pa and argon atmosphere, generate low-temperature plasma with radio frequency power of 120W and frequency of 13.56MHz to irradiate the surface of the flame retardant powder for 240 seconds to obtain the surface-activated flame retardant.

[0027] (2) Dissolve 2.5g of KH-560, 4.8g of 2-hydroxymethyl-15-crown-5, and 3.2g of hydroxymethyl-18-crown-6 in 260g of anhydrous ethanol, add 0.3g of triethylamine, and stir for 30 minutes under nitrogen atmosphere protection and temperature of 60℃; then add 1.0g of deionized water to the reaction solution, stir evenly, and prepare a coupling agent deposition solution; immerse the surface-activated flame retardant obtained in step (1) into the coupling agent deposition solution, and stir for 110 minutes under nitrogen atmosphere protection and temperature of 75℃; after the reaction is completed, filter, wash the filter cake with anhydrous ethanol, and then cure for 50 minutes under nitrogen atmosphere and temperature of 110℃ to obtain a flame retardant intermediate with a surface-bonded crown ether structure.

[0028] (3) Add the flame retardant intermediate obtained in step (2) to 2400g of deionized water, stir and soak for 75 minutes at a temperature of 60℃, an ultrasonic frequency of 35kHz and an ultrasonic power of 300W. During the soaking process, take a sample every 15 minutes to measure the conductivity of the soaking solution. When the change in the two measured values ​​at the 60th and 75th minutes is 3.8%, which is less than 5%, stop the soaking. After the soaking is completed, filter, rinse the filter cake with deionized water, and vacuum dry at 80℃ for 10 hours to obtain the low ion precipitation type halogen-free flame retardant.

[0029] Example 3 This embodiment provides a low-ion precipitation type halogen-free flame retardant for electronic products, the preparation method of which includes the following steps: (1) Take 200g of melamine cyanurate powder and spread it evenly on the sample stage of the low-temperature plasma treatment equipment with a thickness of 6mm. Under the conditions of vacuum degree 40Pa and nitrogen atmosphere, generate low-temperature plasma with radio frequency power of 90W and frequency of 13.56MHz to irradiate the surface of the flame retardant powder for 150 seconds to obtain the surface-activated flame retardant.

[0030] (2) Dissolve 3.5g of KH-560, 6.2g of 2-hydroxymethyl-15-crown-5, and 7.8g of hydroxymethyl-18-crown-6 in 420g of anhydrous ethanol, add 0.5g of triethylamine, and stir for 50 minutes under argon atmosphere protection and temperature of 50℃; then add 1.7g of deionized water to the reaction solution, stir evenly, and prepare a coupling agent deposition solution; immerse the surface-activated flame retardant obtained in step (1) into the coupling agent deposition solution, and stir for 95 minutes under argon atmosphere protection and temperature of 82℃; after the reaction is completed, filter, wash the filter cake with anhydrous ethanol, and then cure for 80 minutes under argon atmosphere and temperature of 100℃ to obtain a flame retardant intermediate with a surface-bonded crown ether structure.

[0031] (3) Add the flame retardant intermediate obtained in step (2) to 1800g of deionized water, stir and soak for 50 minutes at a temperature of 72℃, an ultrasonic frequency of 25kHz and an ultrasonic power of 180W. During the soaking process, take a sample every 15 minutes to measure the conductivity of the soaking solution. When the change in the two measured values ​​at the 30th minute and the 45th minute is 4.1%, which is less than 5%, stop the soaking. After the soaking is completed, filter, rinse the filter cake with deionized water, and vacuum dry at 90℃ for 7 hours to obtain the low ion precipitation type halogen-free flame retardant.

[0032] Comparative Example 1 The difference between this comparative example and Example 1 is that step (2) has been omitted. The specific steps are as follows: (1) Take 200g of aluminum diethylphosphinate powder and spread it evenly on the sample stage of the low-temperature plasma treatment equipment with a spreading thickness of 5mm. Under the conditions of vacuum degree 30Pa and nitrogen atmosphere, generate low-temperature plasma with radio frequency power of 100W and frequency of 13.56MHz to irradiate the surface of the flame retardant powder for 180 seconds to obtain the surface-activated flame retardant.

[0033] (2) Add the surface-activated flame retardant to 2000g of deionized water and stir and soak for 60 minutes at a temperature of 65℃, an ultrasonic frequency of 28kHz and an ultrasonic power of 250W. After soaking, filter the mixture, rinse the filter cake with deionized water, and vacuum dry it at 85℃ for 8 hours to obtain the halogen-free flame retardant.

[0034] Comparative Example 2 This comparative example provides a halogen-free flame retardant, the preparation method of which includes the following steps: (1) Take 200g of aluminum diethylphosphonate powder and add it to 800g of deionized water. Heat it to 85°C while stirring to partially dissolve and fully disperse the flame retardant. Continue stirring at this temperature for 60 minutes. After stirring, filter while hot to remove insoluble matter. Cool the filtrate to 10°C at a rate of 2°C / min to precipitate crystals. Filter, wash the filter cake with deionized water, and vacuum dry at 85°C for 8 hours to obtain the recrystallized and purified flame retardant.

[0035] (2) Mix 10g of γ-glycidyl etheroxypropyltrimethoxysilane (KH-560) with 250g of anhydrous ethanol, add 1g of deionized water, stir evenly, and prepare a coupling agent treatment solution; immerse the flame retardant obtained in step (1) with all the recrystallized and purified flame retardant into the coupling agent treatment solution, and stir and react for 100 minutes under nitrogen atmosphere protection and temperature of 80℃; after the reaction is completed, filter, wash the filter cake with anhydrous ethanol, and then cure for 60 minutes under nitrogen atmosphere and temperature of 105℃ to obtain halogen-free flame retardant.

[0036] Comparative Example 3 The difference between this comparative example and Example 1 is as follows: Step (1) is: Take 200g of aluminum diethylphosphonate powder, immerse it in 800g of hydrogen peroxide solution with a mass concentration of 15%, stir and treat it for 120 minutes at a temperature of 60℃, filter it, wash it repeatedly with deionized water until the washing liquid is neutral, and vacuum dry it at 85℃ for 8 hours to obtain a surface-activated flame retardant.

[0037] The remaining steps are the same as in Example 1.

[0038] Comparative Example 4 The difference between this comparative example and Example 1 is as follows: Step (2) is: KH-560 3g, 2-hydroxymethyl-15-crown-5 5g, hydroxymethyl-18-crown-6 5g are mixed with 260g of deionized water, and 1.3g of glacial acetic acid is added to adjust the pH to about 4.5. The mixture is stirred evenly to prepare a coupling agent deposition solution. The flame retardant obtained in step (1) is immersed in the coupling agent deposition solution and stirred for 100 minutes under nitrogen atmosphere protection and temperature of 80°C. After the reaction is completed, the mixture is filtered, the filter cake is washed with anhydrous ethanol, and then cured for 60 minutes under nitrogen atmosphere and temperature of 105°C to obtain the flame retardant intermediate.

[0039] The remaining steps are the same as in Example 1.

[0040] Performance testing The following performance tests were conducted on the flame retardants prepared in Examples 1-3 and Comparative Examples 1-4, and the polyhexamethylene adipamide (PA66) composite materials containing the flame retardants: (1) Content of water-soluble sodium and potassium ions: The content was determined in accordance with the provisions of GB / T 30903-2014 "Determination of impurity elements in inorganic chemical products by inductively coupled plasma mass spectrometry (ICP-MS)". The flame retardant sample was soaked in deionized water at 85°C for 168 hours, and the leachate was analyzed by ICP-MS.

[0041] (2) Surface resistivity retention rate after damp heat aging: Flame retardant was added to PA66 at a mass percentage of 20%, and the mixture was melt-blended and injection-molded using a twin-screw extruder to prepare test samples. In accordance with the provisions of GB / T 31838.2-2019 "Dielectric and resistive properties of solid insulating materials - Part 2: Resistive properties (DC method) - Volume resistivity and volume resistivity", the surface resistivity of the samples was measured in the initial state and after aging for 168 hours at 85°C and 85% relative humidity. The surface resistivity retention rate (%) was calculated as: surface resistivity after aging / initial surface resistivity × 100%.

[0042] The test results are shown in Table 1.

[0043] Table 1 Performance Test Results

[0044] As can be seen from the above performance test results, the low-ion-emission halogen-free flame retardants prepared in Examples 1-3 achieve deep removal of sodium and potassium ions, inhibit the insulation degradation caused by ion precipitation from the source, and significantly improve the electrical reliability of flame-retardant polymer materials under humid and hot conditions.

[0045] Comparative Example 1 omitted the crown ether silane coupling agent deposition and anchoring step. The flame retardant particles lacked a crown ether trapping layer, and sodium and potassium ions were only partially removed through the physical action of ultrasonic immersion. The residual amount was significantly higher than in the example. After humid heat aging, a large number of free ions dissolved and migrated, forming leakage current channels, leading to a substantial decrease in surface resistivity. Comparative Example 2 used recrystallization purification combined with conventional silane coupling agent surface coating. Recrystallization could initially remove some soluble ionic impurities, but the conventional coupling agent coating layer lacked ion selective trapping and complexation locking functions. Residual ions could still freely dissolve and migrate under humid heat conditions. The sodium and potassium ion content and insulation retention rate were significantly lower than the solution of this invention. Comparative Example 3 used hydrogen peroxide liquid-phase oxidation activation instead of low-temperature plasma activation. Although hydrogen peroxide could introduce oxygen-containing groups onto the flame retardant surface, its activation efficiency and surface active site density were lower than those of low-temperature plasma irradiation treatment. This resulted in a weakened chemical bonding and anchoring effect of the subsequent crown ether silane coupling agent, insufficient density and bonding strength of the cross-linked layer, and a corresponding decrease in ion trapping and locking capabilities. Comparative Example 4 replaced the deposition process of the present invention, which involves dispersion with anhydrous ethanol followed by quantitative addition of water to controllably initiate polycondensation, with a conventional water-acid system. In this case, the coupling agent rapidly hydrolyzes and undergoes bulk polycondensation in the acidic aqueous solution from the moment it comes into contact with the solvent. Some of the coupling agent self-polymerizes into oligomers in the solution and fails to effectively anchor to the flame retardant surface. At the same time, due to the lack of a pre-reaction step, the ring-opening grafting between KH-560 and hydroxymethyl crown ether is not completed in advance. The crown ether molecules are mainly physically mixed into the cross-linking network rather than being covalently bonded and fixed. The integrity and density of the cross-linking layer are damaged, the effective density of crown ether trapping sites is reduced, and the ion precipitation suppression effect and insulation retention performance are affected.

[0046] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles 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 low-ion precipitation type halogen-free flame retardant for electronic products, characterized in that, Includes the following steps: (1) Spread phosphorus-nitrogen halogen-free flame retardant powder on the sample stage of a low-temperature plasma treatment device, and irradiate the surface of the flame retardant powder under vacuum of 10~50Pa and inert atmosphere to obtain a surface-activated flame retardant. (2) Dissolve the silane coupling agent with 2-hydroxymethyl-15-crown-5 and hydroxymethyl-18-crown-6 in anhydrous ethanol, add triethylamine, and perform a pre-reaction. Then add deionized water to the reaction solution, stir, and prepare a coupling agent deposition solution. Immerse the surface-activated flame retardant obtained in step (1) into the coupling agent deposition solution and stir the reaction under an inert atmosphere. After the reaction is completed, filter, wash with anhydrous ethanol, and then cure under an inert atmosphere and at a temperature of 90~120℃ to obtain a flame retardant intermediate with a surface-bonded crown ether structure. (3) Add the flame retardant intermediate obtained in step (2) to deionized water, stir and soak under ultrasonic conditions; after soaking, filter, rinse the filter cake with deionized water, and dry to obtain the low ion precipitation type halogen-free flame retardant.

2. The preparation method of the low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, In step (1), the phosphorus-nitrogen halogen-free flame retardant is selected from any one or a mixture of several of aluminum hypophosphite, aluminum diethylphosphite, melamine polyphosphate, and melamine cyanurate.

3. The method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, In step (1), the phosphorus-nitrogen halogen-free flame retardant powder is spread to a thickness of 3-8 mm on the sample stage of the low-temperature plasma treatment equipment; the irradiation treatment time is 120-300 seconds.

4. The method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, In step (2), the silane coupling agent is 3-glycidoxypropyltrimethoxysilane; the mass ratio of the total mass of the silane coupling agent, 2-hydroxymethyl-15-crown-5, and hydroxymethyl-18-crown-6 to anhydrous ethanol is 1:20~35; the mass of the deionized water is 5%~15% of the total mass of the silane coupling agent, 2-hydroxymethyl-15-crown-5, and hydroxymethyl-18-crown-6; and the amount of triethylamine added is 1%~5% of the total mass of the silane coupling agent, 2-hydroxymethyl-15-crown-5, and hydroxymethyl-18-crown-6.

5. The method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, In step (2), the mass ratio of hydroxymethyl-18-crown-6 to 2-hydroxymethyl-15-crown-5 is 1:0.5~2.0; the amount of silane coupling agent is 20%~50% of the total mass of 2-hydroxymethyl-15-crown-5 and hydroxymethyl-18-crown-6; and the total amount of silane coupling agent, 2-hydroxymethyl-15-crown-5 and hydroxymethyl-18-crown-6 is 3%~9% of the mass of flame retardant.

6. The method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, In step (2), the temperature of the pre-reaction is 40~60℃ and the time of the pre-reaction is 30~60 minutes.

7. The method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, The temperature of the stirring reaction in step (2) is 70~85℃, and the stirring reaction time is 90~120 minutes.

8. The method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, In step (3), the mass ratio of the flame retardant intermediate to deionized water is 1:8~15.

9. The method for preparing a low-ion precipitation type halogen-free flame retardant for electronic products according to claim 1, characterized in that, In step (3), the conductivity of the immersion solution is measured every 15 minutes during the immersion process. The immersion is terminated when the change in two consecutive measurements is no more than 5% of the last measurement.

10. A low-ion precipitation type halogen-free flame retardant for electronic products, characterized in that, It is obtained by the preparation method of the low-ion precipitation type halogen-free flame retardant for electronic products as described in any one of claims 1-9.

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