An alkoxy anchoring agent for thermally conductive powder, its synthesis method and application

Abstract

This invention discloses an alkoxy anchoring agent for thermally conductive powders, its synthesis method, and its application, relating to the field of thermally conductive composite materials technology. The molecular structural formula of the alkoxy anchoring agent for thermally conductive powders is as follows: R-(MeHSiO) a (Me2SiO) x (MePhSiO) b (MeBuSiO) c -Si(CH2)3Si(OCH3)3; where R is one of butyl, octyl, or dodecyl, a is a natural number from 1 to 4, x is a natural number from 12 to 46, b is a natural number from 1 to 5, and c is a natural number from 1 to 5. This alkoxy anchoring agent can significantly reduce the processing viscosity of thermally conductive composite materials, inhibit the precipitation of small molecules, and improve aging resistance. It is suitable for thermal interface materials in high-end equipment such as optical modules and high-performance chips.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive composite materials technology, specifically to an alkoxy anchoring agent, its synthesis method, and its application, which can be applied to ultra-high thermal conductivity materials to reduce the viscosity of thermally conductive materials during processing to improve processing efficiency, and at the same time greatly reduce the probability of oil-powder separation in thermally conductive composite materials during long-term use or under extreme environments, thereby extending their service life. Background Technology

[0002] As equipment rapidly evolves towards high performance, high integration, and high reliability, the heat density of its core units, such as power devices, computing chips, and optoelectronic modules, is increasing exponentially. Thermal management has become a common key technological bottleneck restricting the performance improvement, lifespan extension, and reliability assurance of high-end equipment. Particularly in fields such as 5G / 6G communication, data centers, and high-performance computing, the heat dissipation problem of optical modules (especially high-speed, high-power modules such as 400G / 800G / 1.6T, and advanced packaging forms such as CPO / NPO) is becoming increasingly severe. With the increase in speed, the power consumption and heat generation of its core electro-optic / optoelectronic conversion components increase exponentially, and these "heat sources" are tiny, resulting in extremely high heat flux density. At the same time, the standardized size of optical modules and extremely limited internal space lead to the close arrangement of multiple heat sources, making heat accumulation easy and difficult to dissipate naturally through air convection. For the specific application scenarios of optical modules, in addition to high thermal conductivity, very stringent and multi-dimensional requirements are put forward for the internal thermal interface material (TIM): low application pressure / low hardness to avoid crushing the chip or damaging the substrate; low oil leakage / low precipitation to avoid contaminating sensitive optical components (such as lenses and fiber end faces) and causing optical path performance degradation; weather resistance and stability, the material must not harden, crack, pulverize or soften excessively and be lost, and must maintain stable performance.

[0003] However, existing thermal conductive materials on the market struggle to simultaneously meet the requirements of low hardness, low oil exudation, and heat resistance stability in current and future high-end equipment applications. On one hand, conventional silane coupling agents used in formulations are prone to volatilization and failure at high temperatures, leading to hardening or even powdering and cracking of the thermal pad material after exposure to high temperatures. In recent years, alkoxy-modified low-molecular-weight silicone oils have been used as powder treatment agents, resulting in improved temperature resistance. However, most current alkoxy-modified low-molecular-weight silicone oils have methyl, alkyl, vinyl, or ether groups in their molecular chains, in addition to alkoxy groups. To control low hardness in low-hardness, high-conductivity thermal pads, the vinyl content is often excessive, resulting in a large number of free vinyl silicone oil molecules. Existing alkoxy-modified low-molecular-weight silicone oils cannot react with the excess vinyl silicone oil to form effective chemical bonds, thus lacking a stable chemical anchoring connection between the powder and the organosilicon molecular chain, and failing to lock in the free vinyl silicone oil molecules. The prepared thermal pads or thermal gels are extremely prone to oil-powder separation, leading to material cracking and the precipitation of small molecule silicone oil. This is a fatal flaw in high-end equipment applications such as aerospace, military electronics, and precision optics, where reliability and cleanliness are extremely important.

[0004] Therefore, developing an anchoring agent that can chemically bond thermally conductive powder to organosilicon molecules, reduce the release rate of organosilicon molecules, and improve the anti-aging performance of flexible organosilicon vinyl addition-type thermally conductive materials in high-end equipment applications can effectively solve the heat dissipation problem of balancing application reliability in this field, and is of great significance for improving the overall performance of high-end equipment. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide an alkoxy anchoring agent for thermally conductive powder, its synthesis method, and its application. This alkoxy anchoring agent for thermally conductive powder has multifunctional, gradient, and sequence-controllable structural characteristics, and can anchor and connect thermally conductive powder with organosilicon molecules through chemical bonds, thereby reducing the exudation rate of organosilicon molecules and improving the anti-aging performance of thermally conductive composite materials.

[0006] This invention provides the following technical solution: In a first aspect, the present invention provides an alkoxy anchoring agent for thermally conductive powders, the molecular structure of which is shown in the following formula (1): R-(MeHSiO) a (Me2SiO) x (MePhSiO) b (MeBuSiO) c -Si(CH2)3Si(OCH3)3 formula (1); Wherein, R is one of butyl, octyl, and dodecyl, a is a natural number from 1 to 4, x is a natural number from 12 to 46, b is a natural number from 1 to 5, and c is a natural number from 1 to 5.

[0007] Secondly, the present invention also provides a synthesis process for the above-mentioned alkoxy anchoring agent for thermally conductive powder, which includes the following steps: S1. Under inert gas protection, dissolve alkyl dimethylchlorosilane in dry toluene, cool to 0-6℃, add tetramethylammonium hydroxide solution dropwise, and after the reaction, allow it to naturally warm to room temperature while stirring. S2. Add methyl hydrogen cyclosiloxane and stir at room temperature to allow it to undergo ring-opening polymerization, thereby obtaining a short-chain polymer with active ends and silane close to the octyl group. S3. Add the dried monomer mixture and heat to 75-95℃ with stirring to react; the monomer mixture is a mixture of octamethylcyclotetrasiloxane, methylphenylcyclosiloxane and methylbutylcyclosiloxane; S4. After cooling to room temperature, add allyl dimethylchlorosilane, stir, and reflux. S5. Add acetic acid to neutralize the tetramethylammonium hydroxide alcohol solution, filter, and distill under reduced pressure to obtain the terminal allyl silicone oil intermediate. S6. The terminal allyl silicone oil intermediate is subjected to a hydrosilylation reaction with trimethoxysilane in the presence of a platinum catalyst. S7. Add activated carbon for adsorption and filtration, and remove excess trimethoxysilane by vacuum distillation to obtain alkoxy anchoring agent.

[0008] Furthermore, the molar proportions of each raw material are based on the amount of alkyl dimethylchlorosilane used as one part: The amount of the methyl hydrogen cyclosiloxane used is 0.5-0.85 parts; The amount of the octamethylcyclotetrasiloxane used is 4-6 parts; The amount of the methylphenylcyclosiloxane used is 0.11-0.18 parts; The amount of the methylbutylcyclosiloxane used is 0.1-0.15 parts; The amount of allyl dimethylchlorosilane used is 1.1-1.2 parts; The amount of the trimethoxysilane used is 1.21-1.32 parts; The amount of the tetramethylammonium hydroxide alcohol solution used is 0.9-1.0 parts; The amount of acetic acid used is 0.02-0.05 parts; The amount of dried toluene used is 3-5 parts.

[0009] Further, in step S1, the alkyl dimethylchlorosilane is selected from one of octyl dimethylchlorosilane, butyl dimethylchlorosilane, and dodecyl dimethylchlorosilane.

[0010] Preferably, in step S1, the drying method for the dried toluene is as follows: under dry nitrogen conditions, toluene is distilled by reflux distillation using CaH2 to obtain dried toluene.

[0011] Preferably, in step S1, the tetramethylammonium hydroxide solution is dripped over 0.5-1 hour, the stirring speed is 20-60 r / min, and the stirring time is 1 hour.

[0012] Further, in step S2, the methyl hydrogen cyclosiloxane is selected from one of methyl hydrogen cyclotrisiloxane and methyl hydrogen cyclotetrasiloxane.

[0013] Preferably, in step S2, the room temperature is 24-30℃; the stirring speed is 20-60 r / min, and the stirring time is 3-6 hours.

[0014] Further, in step S3, the methylbutylcyclosiloxane is selected from methylbutylcyclotrisiloxane and methylbutylcyclotetrasiloxane.

[0015] Further, in step S3, the methylphenylcyclosiloxane is selected from methylphenylcyclotrisiloxane and methylphenylcyclotetrasiloxane.

[0016] Further, in step S3, the tetramethylammonium hydroxide alcohol solution is a methanol solution with a tetramethylammonium hydroxide concentration of 20%-25%.

[0017] Further, in step S3, the drying process is as follows: octamethylcyclotetrasiloxane, methylphenylcyclosiloxane and methylbutylcyclosiloxane are mixed in proportion and added to a storage bottle containing molecular sieves, and then allowed to stand for 14-48 hours to dry and remove water.

[0018] Preferably, in step S3, the stirring speed is 90-160 r / min and the stirring time is 6-12 hours.

[0019] Furthermore, in step S4, the stirring speed is 90-160 r / min, and the time is 1-4 hours.

[0020] Further, in step S5, the reaction time for the acetic acid to neutralize the tetramethylammonium hydroxide solution is 15-30 minutes. The temperature of the vacuum distillation is 80-110℃, and the pressure is <5 mmHg.

[0021] Further, in step S6, the terminal allyl silicone oil intermediate and trimethoxysilane are mixed at a molar ratio of C=C:Si-H=1:1.1, and then stirred at a speed of 60-110 r / min. During the stirring process, a platinum catalyst is added dropwise. After the addition is completed, the mixture is stirred at 60-110 r / min at 50-80℃ for 1-6 hours.

[0022] Further, in step S6, the platinum catalyst is a caster platinum catalyst or a chloroplatinic acid catalyst, and the platinum content is 1-5 ppm.

[0023] Furthermore, in step S7, the temperature of the vacuum distillation is 60-80℃, and the time is 1-2 hours.

[0024] Furthermore, the synthesis process of the alkoxy anchoring agent for the thermally conductive powder is completed in an inert gas protective atmosphere, preferably nitrogen or argon.

[0025] Thirdly, the present invention also provides the application of the above-mentioned alkoxy anchoring agent for thermally conductive powder in the preparation of thermally conductive composite materials.

[0026] Preferably, the thermally conductive composite material is a thermally conductive pad composite material or a thermally conductive gel composite material.

[0027] Fourthly, the present invention also provides a thermally conductive pad composite material comprising the above-mentioned alkoxy anchoring agent.

[0028] Furthermore, the thermally conductive pad composite material is prepared from the following raw materials in parts by weight: 100 parts of vinyl-terminated silicone oil; Hydrogen-containing silicone oil 0.4-3 parts; Polymerization inhibitor 0.01-0.06 parts; Pigment 0.2-0.6 parts; Catalyst 0.1-0.5 parts; Alkoxy anchoring agent 0.6-2.2 parts; 18-25 parts of thermally conductive powder filler; The thermally conductive powder filler is a mixture of spherical alumina, spherical alumina and spherical aluminum nitride powder.

[0029] Preferably, the mass ratio of the spherical alumina, spherical alumina and spherical aluminum nitride is (10-20):(20-40):(40-70).

[0030] Preferably, the spherical alumina has a medium particle size of 2 micrometers, the spherical alumina has a medium particle size of 10 micrometers, and the spherical aluminum nitride has a medium particle size of 80 micrometers.

[0031] The viscosity of the vinyl-terminated silicone oil is 50-250 cp.

[0032] The hydrogen-containing silicone oil is a side-containing hydrogen-containing silicone oil with a hydrogen content of 0.1%-0.36%.

[0033] The polymerization inhibitor is an alkynyl alcohol-based polymerization inhibitor.

[0034] The colorant is selected from either iron oxide red or carbon black.

[0035] The catalyst is a Castrol platinum catalyst with a concentration of 1000-5000 ppm.

[0036] Fifthly, the present invention also provides a method for preparing the above-mentioned thermally conductive pad composite material, comprising the following steps: According to the formula, the vinyl silicone oil, hydrogen-containing silicone oil, polymerization inhibitor, colorant and alkoxy anchoring agent are added into the reaction vessel and stirred under vacuum at a speed of 10-90 rpm for 15-60 min. Add half the mass of thermally conductive powder filler and vacuum stir at 10-90 rpm for 15-60 min; Add the remaining thermally conductive powder filler and vacuum stir at 10-90 rpm for 15-60 min; Add the catalyst and stir under vacuum at 10-90 rpm for 15-60 minutes to obtain a slurry. During this step, the cooling water should be turned on to cool the material in the reactor. The temperature of the cooling water should be 0-10℃.

[0037] After mixing, the slurry is placed in a mold and cured at 90-105℃ to complete the preparation of the thermal pad composite material.

[0038] The present invention has the following technical effects: The alkoxy anchoring agent of this invention achieves multifunctional anchoring through a unique molecular structure design. One end has a trimethoxy structure, which can modify the powder surface and connect with the hydroxyl active groups on the powder surface, establishing a chemical bridge between the filler and the silicone oil. The other end has an alkyl group, which has good affinity with silicone resin and thermally conductive filler. The silanol groups distributed on the side chains directly participate in the formation of a chemical cross-linking network during the curing process of the thermally conductive pad composite material, flexibly connecting the thermally conductive filler powder with the vinyl silicone oil, preventing the migration and leakage of the filler itself and excess vinyl silicone oil molecules within the system. Simultaneously, the phenyl groups distributed on the side chains impart a higher thermal decomposition temperature to the chain segments, improving the thermal reliability of the thermally conductive pad composite material. The butyl groups distributed on the side chains, as long-chain alkyl groups, enhance the hydrophobicity of the system, allowing for fine-tuning of the polarity of the silicone oil and its wettability with the powder. Furthermore, its flexibility is superior to that of phenyl groups, helping to maintain a certain degree of flexibility within rigid chain segments.

[0039] Meanwhile, the synthesis process of alkoxy anchoring agents, through sequential feeding and gradient reaction control, endows the anchoring agents with a unique sequence structure, thereby achieving excellent application performance. First, a sequential feeding process is adopted, adding hydrogen-containing monomers first, followed by mixed monomers. This ensures that the silane groups are concentrated near the alkyl ends of the molecular chain, enabling them to efficiently participate in the crosslinking reaction during curing, firmly anchoring the thermally conductive filler to the vinyl silicone oil, while avoiding excessive crosslinking that could affect the material's flexibility. Second, phenyl and butyl monomers are introduced by mixing and then adding them, ensuring a regular and uniform distribution in the main chain. Phenyl imparts excellent thermal stability to the molecular chain segments, improving the reliability of the composite material under high-temperature conditions; butyl, as a long-chain alkyl group, enhances the system's hydrophobicity and powder wettability, while introducing flexibility into the rigid chain segments, forming a flexible polymer layer around the filler. This effectively absorbs interfacial stress generated by thermal cycling or mechanical stress, preventing interfacial cracking. Finally, a hydrosilylation reaction is used to efficiently introduce trimethoxysilane, which exhibits good selectivity and does not attack the side-chain silanes, ensuring that the anchoring agent retains a complete trimethoxy structure at one end. This allows it to form a stable chemical bond with the hydroxyl groups on the powder surface, establishing a strong interfacial bridge between the filler and the organosilicon matrix. This synthesis process is simple, uses readily available raw materials, and is easily industrialized. The resulting anchoring agent does not require pretreatment of the powder and can be directly added to the formulation for simultaneous mixing, simplifying the production process. Ultimately, a thermally conductive composite material with moderate slurry viscosity, excellent aging resistance, and extremely low small molecule precipitation rate is obtained.

[0040] The alkoxy anchoring agent of this invention does not require pre-treatment of the powder; it can be directly added to the thermal pad formulation system for simultaneous mixing, simplifying the production process. The alkoxy anchoring agent is grafted onto the surface of the powder filler, forming a flexible polymer layer around it. This layer effectively absorbs and dissipates interfacial stress generated by heat dissipation cycles or mechanical stress, greatly improving the toughness and long-term reliability of the interface. Attached Figure Description

[0041] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0042] Figure 1 These are the appearance images of the thermal pads provided in Embodiments 1-3 and Comparative Example 1 after Hast aging. Figure 2 This is a diagram showing the appearance of the thermal pad provided in Comparative Example 2 of the present invention after Hast aging. Figure 3 This is a diagram showing the appearance of the thermal pad provided in Comparative Example 3 of the present invention after Hast aging. Figure 4This is a diagram showing the appearance of the thermal pad provided in Comparative Example 4 of the present invention after Hast aging. Figure 5 This is a view of the thermal pad provided in Comparative Example 5 of the present invention after Hast aging. Detailed Implementation

[0043] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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.

[0044] It should be understood that, when used in this specification and the appended claims, the terms “comprising” and “including” indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0045] An alkoxy anchoring agent for thermally conductive powders has the following molecular structure (1): R-(MeHSiO) a (Me2SiO) x (MePhSiO) b (MeBuSiO) c -Si(CH2)3Si(OCH3)3 formula (1); Wherein, R is one of butyl, octyl, and dodecyl, a is a natural number from 1 to 4, x is a natural number from 12 to 46, b is a natural number from 1 to 5, and c is a natural number from 1 to 5.

[0046] It should be noted that the alkoxy anchoring agents prepared by this invention are all mixtures, composed of a series of molecules conforming to the above general formula. The values ​​of a, x, b, and c in each molecular chain vary due to the statistical distribution characteristics of the polymerization reaction, but all molecules conform to the structural characteristics defined by this general formula, that is, one end of the molecular chain is an alkyl group R, the silanol groups are concentrated near the alkyl end, the phenyl and butyl groups are uniformly distributed in the molecular chain, and the other end is a trimethoxysilyl group. The feed ratios and reaction conditions given in the various embodiments are sufficient for those skilled in the art to implement this invention.

[0047] A process for synthesizing the above-mentioned alkoxy anchoring agent for thermally conductive powder includes the following steps: S1. Raw material preparation: Prepare the following raw materials by mass fraction: 1 part of alkyl dimethylchlorosilane: 0.5-0.85 parts of methyl-containing hydrogen cyclosiloxane; 4-6 parts of octamethylcyclotetrasiloxane; 0.11-0.18 parts of methylphenylcyclosiloxane; 0.1-0.15 parts of methylbutylcyclosiloxane; 1.1-1.2 parts of allyl dimethylchlorosilane; 1.21-1.32 parts of trimethoxysilane; 0.9-1.0 parts of tetramethylammonium hydroxide alcohol solution; Acetic acid 0.02-0.05 parts; 3-5 parts of dried toluene.

[0048] S2. Under inert gas protection, add alkyl dimethylchlorosilane to a reaction flask containing dry toluene, cool to 0-6℃, slowly add tetramethylammonium hydroxide alcohol solution dropwise using a dry syringe, and complete the addition in 0.5-1 hour. Allow the mixture to naturally warm to room temperature and stir at 20-60 r / min for 1 hour. S3. Slowly add methyl hydrogen cyclosiloxane according to the metered amount using a dry constant pressure funnel, and stir at 20-60 r / min for 3-6 hours at room temperature (24-30℃) to allow it to undergo ring-opening polymerization, thereby obtaining a short-chain polymer with active ends and silane close to the octyl group. S4. Mix octamethylcyclotetrasiloxane, methylphenylcyclosiloxane and methylbutylcyclosiloxane and add them to a storage bottle containing molecular sieves. Let stand for 14-48 hours to dry and remove water to obtain a dry monomer mixture. Add the monomer mixture to the reaction solution after the reaction in step S3, heat to 75-95℃, and stir at 90-160 r / min for 6-12 hours. S5. After cooling to room temperature, add allyl dimethylchlorosilane dropwise to the reaction solution after the reaction in step S4 is completed, and stir at a speed of 20-60 r / min for 1-4 hours, while refluxing during stirring. S6. Add acetic acid and react for 15-30 minutes to neutralize and decompose the tetramethylammonium hydroxide alcohol solution, thus deactivating it; filter to remove the generated salt; heat the filtrate to 80-110℃, set the pressure to <5mmHg, and distill the filtrate under reduced pressure in a rotary evaporator or short-path distillation apparatus to remove the solvent and unreacted low-boiling-point monomers, and obtain a pure terminal allyl silicone oil intermediate. S7. Under inert gas protection, the terminal allyl silicone oil intermediate and trimethoxysilane are mixed at a molar ratio of C=C:Si-H=1:1.1 and stirred at a speed of 60-110 r / min. While stirring, platinum catalyst is added dropwise. After the addition is completed, the reaction is continued at 50-80℃ with a stirring speed of 60-110 r / min for 1-6 hours to carry out the hydrosilylation reaction. S8. Add 1%-6% of activated carbon (based on the total mass of the reaction solution after step S7) for adsorption and filtration to remove the platinum catalyst. Heat the filtrate to 60-80℃ and perform vacuum distillation for 1-2 hours to remove excess trimethoxysilane, obtaining the alkoxy anchoring agent.

[0049] A method for preparing a thermally conductive pad composite material includes the following steps: (1) Raw material preparation; Prepare the following raw materials according to the mass proportions: 100 parts of vinyl silicone oil with a viscosity of 50-250 cp; The hydrogen-containing silicone oil is 0.4-3 parts of a side-containing hydrogen silicone oil with a hydrogen content of 0.1%-0.36%; The polymerization inhibitor is an alkynyl alcohol-based polymerization inhibitor, 0.01-0.06 parts; The pigment is 0.2-0.6 parts of iron oxide red or carbon black; The catalyst is 0.1-0.5 parts of a Castrol platinum catalyst with a concentration of 1000-5000 ppm; Alkoxy anchoring agent 0.6-2.2 parts; 18-25 parts of thermally conductive powder filler; The thermally conductive powder filler is composed of the following components by mass percentage: 10%-20% 2-micron spherical alumina, 20%-40% 10-micron spherical alumina, and 40%-70% 80-micron spherical aluminum nitride. (2) Add the vinyl silicone oil, hydrogen-containing silicone oil, polymerization inhibitor, pigment, and alkoxy anchoring agent into a 60L reactor according to the ratio, and stir under vacuum at a speed of 10-90rpm for 15-60min. (3) Add half the mass of thermally conductive powder filler and vacuum stir at 10-90 rpm for 15-60 min; (4) Add the remaining thermally conductive powder filler and vacuum stir at a speed of 10-90 rpm for 15-60 min; (5) Add catalyst and vacuum stir at 10-90 rpm for 15-60 min to obtain slurry; during this step, cooling water needs to be turned on to cool the material in the reactor. The temperature of the cooling water is 0-10℃. (6) After stirring, take the slurry into the mold and place it in an oven at 90-105℃ to solidify and shape, thus completing the preparation of the thermal pad composite material.

[0050] Example 1 An alkoxy anchoring agent for thermally conductive powders has a molecular structure that conforms to the following formula (1): R-(MeHSiO) a (Me2SiO) x (MePhSiO)b (MeBuSiO) c -Si(CH2)3Si(OCH3)3 formula (1); Where R is a sigma, a is a natural number from 1 to 4, x is a natural number from 12 to 46, b is a natural number from 1 to 5, and c is a natural number from 1 to 5.

[0051] A process for synthesizing the above-mentioned alkoxy anchoring agent for thermally conductive powder includes the following steps: S1. Raw material preparation: Prepare the following raw materials by mass fraction: 1 part of octyl dimethylchlorosilane: 0.65 parts of methyl-containing hydrogen cyclosiloxane; 4 parts of octamethylcyclotetrasiloxane; 0.14 parts of methylphenylcyclosiloxane; 0.13 parts of methylbutylcyclosiloxane; 1.1 parts of allyl dimethylchlorosilane; 1.26 parts of trimethoxysilane; 0.9 parts of tetramethylammonium hydroxide alcohol solution; Acetic acid 0.03 parts; 4 parts of dried toluene.

[0052] S2. Under inert gas protection, add octyl dimethylchlorosilane to a reaction flask containing dry toluene, cool to 0-6℃, and slowly add tetramethylammonium hydroxide solution dropwise using a dry syringe. The addition is completed in 0.5 hours. Allow the mixture to naturally warm to room temperature and stir at 30 r / min for 1 hour. S3. Slowly add methyl hydrogen cyclosiloxane according to the metered amount using a dry constant pressure funnel, and stir at 30 r / min for 4 hours at room temperature to allow it to undergo ring-opening polymerization, thereby obtaining a short-chain polymer with active ends and silane close to the octyl group. S4. Mix octamethylcyclotetrasiloxane, methylphenylcyclosiloxane and methylbutylcyclosiloxane and add them to a storage bottle containing molecular sieves. Let stand for 24 hours to dry and remove water to obtain a dry monomer mixture. Add the monomer mixture to the reaction solution after the reaction in step S3, heat to 85°C and stir at 120 r / min for 9 hours. S5. After cooling to room temperature, add allyl dimethylchlorosilane dropwise to the reaction solution after the reaction in step S4 is completed, and stir at 40 r / min for 3 hours while refluxing. S6. Add acetic acid and react for 22 min to neutralize and decompose the tetramethylammonium hydroxide alcohol solution, thus deactivating it; filter to remove the generated salt; heat the filtrate to 95℃, set the pressure to <5mmHg, and distill the filtrate under reduced pressure in a rotary evaporator or short-path distillation apparatus to remove the solvent and unreacted low-boiling-point monomers, and obtain a pure terminal allyl silicone oil intermediate. S7. Under inert gas protection, the terminal allyl silicone oil intermediate and trimethoxysilane are mixed at a molar ratio of C=C:Si-H=1:1.1 and stirred at a speed of 85 r / min. While stirring, platinum catalyst is added dropwise. After the addition is completed, the reaction is continued at 65°C with a stirring speed of 85 r / min for 3.5 hours to carry out the hydrosilylation reaction. S8. Add 3.5% activated carbon (based on the total mass of the reaction solution after step S7) for adsorption and filtration to remove the platinum catalyst. Heat the filtrate to 70°C and perform vacuum distillation for 1.5 hours to remove excess trimethoxysilane, obtaining the alkoxy anchoring agent.

[0053] A method for preparing a thermally conductive pad composite material includes the following steps: Raw material preparation; Prepare the following raw materials according to the specified weight proportions: 100 parts of vinyl silicone oil with a viscosity of 250 cp; The hydrogen-containing silicone oil consists of 3 parts of a side-containing hydrogen-containing silicone oil with a hydrogen content of 0.1%; The polymerization inhibitor is 0.01-0.06 parts of ethynylcyclohexanol; The colorant is 0.2-0.6 parts carbon black; The catalyst is 0.1-0.5 parts of a 5000 ppm Castrol platinum catalyst; Alkoxy anchoring agent 0.6-2.2 parts; 18-25 parts of thermally conductive powder filler; The thermally conductive powder filler is composed of the following components by mass percentage: 20% 2-micron spherical alumina, 30% 10-micron spherical alumina, and 50% 80-micron spherical aluminum nitride. (2) Add the vinyl silicone oil, hydrogen-containing silicone oil, polymerization inhibitor, pigment, and alkoxy anchoring agent into a 60L reactor according to the ratio, and stir under vacuum at 10rpm for 60min. (3) Add half the mass of thermally conductive powder filler and vacuum stir at 10 rpm for 60 min; (4) Add the remaining thermally conductive powder filler and vacuum stir at 10 rpm for 60 min; (5) Add catalyst and vacuum stir at 10 rpm for 60 min to obtain slurry; during this step, cooling water needs to be turned on to cool the material in the reactor. The temperature of the cooling water is 5℃. (6) After stirring, take the slurry into the mold and place it in an oven at 105°C to solidify and shape, thus completing the preparation of the thermal pad composite material.

[0054] Example 2 An alkoxy anchoring agent for thermally conductive powders has a molecular structure that conforms to the following formula (1): R-(MeHSiO) a (Me2SiO) x (MePhSiO) b (MeBuSiO) c -Si(CH2)3Si(OCH3)3 formula (1); Where R is butyl, a is a natural number from 1 to 4, x is a natural number from 12 to 46, b is a natural number from 1 to 5, and c is a natural number from 1 to 5.

[0055] A process for synthesizing the above-mentioned alkoxy anchoring agent for thermally conductive powder includes the following steps: S1. Raw material preparation: Prepare the following raw materials by mass fraction: 1 part of butyl dimethylchlorosilane: 0.5 parts of methyl-containing hydrogen cyclosiloxane; 4 parts of octamethylcyclotetrasiloxane; 0.11 parts of methylphenylcyclosiloxane; 0.1 parts of methylbutylcyclosiloxane; 1.1 parts of allyl dimethylchlorosilane; 1.21 parts of trimethoxysilane; 0.9 parts of tetramethylammonium hydroxide alcohol solution; Acetic acid 0.02 parts; 3 parts of dried toluene.

[0056] S2. Under inert gas protection, butyl dimethylchlorosilane was added to a reaction flask containing dry toluene. The temperature was lowered to 0-6℃, and tetramethylammonium hydroxide solution was slowly added dropwise using a dry syringe. The addition was completed in 0.5 hours. The temperature was then naturally raised to room temperature, and the mixture was stirred at 20 r / min for 1 hour. S3. Slowly add methyl hydrogen cyclosiloxane according to the metered amount using a dry constant pressure funnel, and stir at 60 r / min for 3 hours at room temperature to allow it to undergo ring-opening polymerization, thereby obtaining a short-chain polymer with active ends and silane close to the octyl group. S4. Mix octamethylcyclotetrasiloxane, methylphenylcyclosiloxane and methylbutylcyclosiloxane and add them to a storage bottle containing molecular sieves. Let stand for 14 hours to dry and remove water to obtain a dry monomer mixture. Add the monomer mixture to the reaction solution after the reaction in step S3, heat to 75°C and stir at 160 r / min for 6 hours. S5. After cooling to room temperature, add allyl dimethylchlorosilane dropwise to the reaction solution after the reaction in step S4 is completed, and stir at 60 r / min for 1 hour while refluxing. S6. Add acetic acid and react for 15 min to neutralize and decompose the tetramethylammonium hydroxide alcohol solution, thus deactivating it; filter to remove the generated salt; heat the filtrate to 80℃, set the pressure to <5mmHg, and distill the filtrate under reduced pressure in a rotary evaporator or short-path distillation apparatus to remove the solvent and unreacted low-boiling-point monomers, and obtain a pure terminal allyl silicone oil intermediate. S7. Under inert gas protection, the terminal allyl silicone oil intermediate and trimethoxysilane are mixed at a molar ratio of C=C:Si-H=1:1.1 and stirred at a speed of 60 r / min. While stirring, platinum catalyst is added dropwise. After the addition is completed, the reaction is continued at 50°C with a stirring speed of 110 r / min for 1 hour to carry out the hydrosilylation reaction. S8. Add 1% activated carbon (based on the total mass of the reaction solution after step S7) for adsorption and filtration to remove the platinum catalyst. Heat the filtrate to 60°C and perform vacuum distillation for 2 hours to remove excess trimethoxysilane, obtaining the alkoxy anchoring agent.

[0057] A method for preparing a thermally conductive pad composite material includes the following steps: (1) Raw material preparation; Prepare the following raw materials according to the mass proportions: 100 parts of vinyl silicone oil with a viscosity of 50 cp; The hydrogen-containing silicone oil is 0.4 parts of a side-containing hydrogen-containing silicone oil with a hydrogen content of 0.36%; The polymerization inhibitor is 0.01 parts of 3,5-dimethyl-1-hexyn-3-ol; The pigment is 0.6 parts of iron oxide red; The catalyst was 0.5 parts of a 1000 ppm Castel platinum catalyst; 2.2 parts of alkoxy anchoring agent; 25 parts of thermally conductive powder filler; The thermally conductive powder filler is composed of the following components by mass percentage: 10% 2-micron spherical alumina, 20% 10-micron spherical alumina, and 70% 80-micron spherical aluminum nitride. (2) Add the vinyl silicone oil, hydrogen-containing silicone oil, polymerization inhibitor, pigment, and alkoxy anchoring agent into a 60L reactor according to the ratio, and stir under vacuum at 90rpm for 15min. (3) Add half the mass of thermally conductive powder filler and vacuum stir at 90 rpm for 15 min; (4) Add the remaining thermally conductive powder filler and vacuum stir at 90 rpm for 15-60 min; (5) Add catalyst and stir under vacuum at 90 rpm for 15 min to obtain slurry; during this step, cooling water needs to be turned on to cool the material in the reactor. The temperature of the cooling water is 5℃. (6) After stirring, take the slurry into the mold and place it in an oven at 90°C to solidify and shape, thus completing the preparation of the thermal pad composite material.

[0058] Example 3 An alkoxy anchoring agent for thermally conductive powders has a molecular structure that conforms to the following formula (1): R-(MeHSiO) a (Me2SiO) x (MePhSiO) b (MeBuSiO) c -Si(CH2)3Si(OCH3)3 formula (1); Where R is dodecyl, a is a natural number from 1 to 4, x is a natural number from 12 to 46, b is a natural number from 1 to 5, and c is a natural number from 1 to 5.

[0059] A process for synthesizing the above-mentioned alkoxy anchoring agent for thermally conductive powder includes the following steps: S1. Raw material preparation: Prepare the following raw materials by mass fraction: 1 part of dodecyl dimethylchlorosilane: 0.85 parts of methyl-containing hydrogen cyclosiloxane; 6 parts of octamethylcyclotetrasiloxane; 0.18 parts of methylphenylcyclosiloxane; 0.15 parts of methylbutylcyclosiloxane; 1.2 parts of allyl dimethylchlorosilane; 1.32 parts of trimethoxysilane; 1.0 part of tetramethylammonium hydroxide alcohol solution; Acetic acid 0.05 parts; 5 parts of dried toluene.

[0060] S2. Under inert gas protection, add alkyl dimethylchlorosilane to a reaction flask containing dry toluene, cool to 0-6℃, slowly add tetramethylammonium hydroxide alcohol solution dropwise using a dry syringe, and finish the addition in 1 hour. Then, allow the temperature to rise naturally to room temperature and stir at 60 r / min for 1 hour. S3. Slowly add methyl hydrogen cyclosiloxane according to the metered amount using a dry constant pressure funnel, and stir at 20 r / min for 6 hours at room temperature to allow it to undergo ring-opening polymerization, thereby obtaining a short-chain polymer with active ends and silane close to the octyl group. S4. Mix octamethylcyclotetrasiloxane, methylphenylcyclosiloxane and methylbutylcyclosiloxane and add them to a storage bottle containing molecular sieves. Let stand for 48 hours to dry and remove water to obtain a dry monomer mixture. Add the monomer mixture to the reaction solution after the reaction in step S3, heat to 95°C, and stir at 90 r / min for 12 hours. S5. After cooling to room temperature, add allyl dimethylchlorosilane dropwise to the reaction solution after the reaction in step S4 is completed, and stir at 20 r / min for 4 hours while refluxing. S6. Add acetic acid and react for 30 min to neutralize and decompose the tetramethylammonium hydroxide alcohol solution, thus deactivating it; filter to remove the generated salt; heat the filtrate to 110℃, set the pressure to <5mmHg, and distill the filtrate under reduced pressure in a rotary evaporator or short-path distillation apparatus to remove the solvent and unreacted low-boiling-point monomers, and obtain a pure terminal allyl silicone oil intermediate. S7. Under inert gas protection, the terminal allyl silicone oil intermediate and trimethoxysilane are mixed at a molar ratio of C=C:Si-H=1:1.1 and stirred at a speed of 110 r / min. While stirring, platinum catalyst is added dropwise. After the addition is completed, the reaction is continued at 80°C with a stirring speed of 60 r / min for 6 hours to carry out the hydrosilylation reaction. S8. Add 6% activated carbon (based on the total mass of the reaction solution after step S7) for adsorption and filtration to remove the platinum catalyst. Heat the filtrate to 80°C and perform vacuum distillation for 1 hour to remove excess trimethoxysilane, obtaining the alkoxy anchoring agent.

[0061] A method for preparing a thermally conductive pad composite material includes the following steps: (1) Raw material preparation; Prepare the following raw materials according to the mass proportions: 100 parts of vinyl silicone oil with a viscosity of 250 cp; The hydrogen-containing silicone oil consists of 3 parts of a side-containing hydrogen-containing silicone oil with a hydrogen content of 0.1%; The polymerization inhibitor is 0.06 parts of ethynylcyclohexanol; The colorant is 0.6 parts carbon black; The catalyst was 0.1 parts of a 5000 ppm Castrol platinum catalyst; 0.6 parts of alkoxy anchoring agent; 18 parts of thermally conductive powder filler; The thermally conductive powder filler is composed of the following components by mass percentage: 20% 2-micron spherical alumina, 40% 10-micron spherical alumina, and 40% 80-micron spherical aluminum nitride. (2) Add the vinyl silicone oil, hydrogen-containing silicone oil, polymerization inhibitor, pigment, and alkoxy anchoring agent into a 60L reactor according to the ratio, and stir under vacuum at 10rpm for 60min. (3) Add half the mass of thermally conductive powder filler and vacuum stir at 10 rpm for 60 min; (4) Add the remaining thermally conductive powder filler and vacuum stir at 10 rpm for 60 min; (5) Add catalyst and vacuum stir at 10 rpm for 60 min to obtain slurry; during this step, cooling water needs to be turned on to cool the material in the reactor. The temperature of the cooling water is 5℃. (6) After stirring, take the slurry into the mold and place it in an oven at 105°C to solidify and shape, thus completing the preparation of the thermal pad composite material.

[0062] To further verify the technical effects of the present invention, comparative examples are set up based on the above embodiment 1 as follows: Comparative Example 1 The only difference between this comparative example and Example 1 is that the alkoxy anchoring agent is replaced in an equal amount with commercially available n-octyltrimethoxysilane (CAS No. 3069-40-7).

[0063] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that the monomer mixture prepared in step S4 lacks methylphenylcyclosiloxane, that is, the final alkoxy anchoring agent molecular chain lacks phenyl compared with Example 1.

[0064] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the monomer mixture prepared in step S4 lacks methyl butyl cyclosiloxane, that is, the final alkoxy anchoring agent molecular chain lacks long-chain alkyl side chains compared with Example 1.

[0065] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the raw material composition lacks methyl hydrogen cyclosiloxane and the preparation process lacks step S3. That is, the final alkoxy anchoring agent molecular chain lacks hydrogen groups in the side chain compared with Example 1.

[0066] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is the difference in steps S3 and S4 during the preparation of the alkoxy anchoring agent. Specifically, in this comparative example, steps S3 and S4 are combined into one step, that is, the mixture of methyl hydrogen-containing cyclosiloxane and monomer is simultaneously added to the reaction solution of the previous step. In this comparative example, the hydrogen groups in the final alkoxy anchoring agent molecular chain exhibit a disordered and random arrangement.

[0067] The following performance characterization tests were performed on the thermal conductive pad composite materials obtained in the examples and comparative examples before curing and on the cured finished products: The viscosity of the uncured slurry was tested according to standard ASTM D4287. Take the cured thermal pad, wrap it with oil-absorbing gauze, and place it in a high-pressure accelerated aging test chamber. Perform accelerated aging test according to standard JESD22-A102E. Set the temperature to 121±2℃ and the humidity to 100±5%RH. After aging for 96 hours, weigh the sample and calculate the mass loss rate after natural drying at room temperature. Use a thermal resistance meter to test the thermal resistance of the sample before and after aging according to ASTM D5470 standard, and calculate the change rate of thermal resistance of the sample after aging.

[0068] The cured thermal pad was placed into a fixture consisting of an aluminum plate on one side and a transparent glass plate on the other. It was compressed by 30% and continuously fixed in a high-pressure accelerated aging test chamber. Accelerated aging tests were conducted according to standard JESD22-A102E, with a temperature of 121±2℃ and a humidity of 100±5%RH. After aging for 96 hours, the appearance of the test sample was observed for cracks. The test results are shown in Table 1 below. Table 1 Performance Characterization Test Results

[0069] As shown in Table 1, the thermal pad slurry prepared in the examples has a moderate viscosity, no cracking after high-pressure accelerated aging test, extremely low weight loss rate, and small thermal resistance change rate, exhibiting excellent processing performance and aging resistance.

[0070] In contrast, Comparative Example 1 used a common silane coupling agent, which resulted in excessively high slurry viscosity. After aging, numerous cracks appeared, leading to a significant increase in weight loss rate and thermal resistance change rate, and severe performance degradation.

[0071] The alkoxy anchoring agent in Comparative Example 2 lacks phenyl groups in its molecular chain, resulting in a certain decrease in temperature resistance. The molecular chain is prone to deterioration during accelerated aging, leading to a significant increase in weight loss after Hast aging. Simultaneously, the bonding between the molecular chain and the thermally conductive filler powder deteriorates, resulting in a looser overall structure and decreased wettability, leading to a larger rate of change in thermal resistance.

[0072] The alkoxy anchoring agent in Comparative Example 3 lacks long-chain alkyl groups, resulting in poor wettability between the organosilicon molecular chain and the powder, leading to a viscous slurry. The reduced flexibility of the molecular chain prevents it from effectively absorbing the interfacial stress between the filler and the resin matrix during accelerated aging, while also weakening its resistance to water penetration, thus generating numerous small cracks. Furthermore, the increased thermal resistance due to the gaps between these cracks contributes to a certain degree of increase in thermal resistance variation.

[0073] The alkoxy anchoring agent in Comparative Example 4 lacks hydrogen groups in its molecular chain, so the vinyl silicone oil, the main component in the thermally conductive pad composite material, cannot play an effective anchoring role. The structure between the molecular chain and the thermally conductive filler powder is easily destroyed during accelerated aging. The excess unreacted vinyl silicone oil is also easy to migrate out due to the lack of effective chemical bond anchoring, resulting in a significant increase in the weight loss rate and thermal resistance change rate after Has aging.

[0074] In Comparative Example 5, the hydrogen groups of the alkoxy anchoring agent molecular chain are randomly distributed on the main chain, which reduces the probability of hydrogen groups binding with vinyl silicone oil. Alternatively, after hydrogen groups preferentially bind with vinyl silicone oil, the binding rate of alkoxy groups with the powder decreases. As a result, the anchoring effect of vinyl silicone oil, the main component of thermally conductive powder and organosilicon, decreases, leading to a significant increase in the weight loss rate and thermal resistance change rate after Has aging.

[0075] The above results indicate that the integrity and specific sequence distribution of phenyl, butyl, and silane groups in the molecular chain of the alkoxy anchoring agent of this invention play a key role in its excellent performance. It can effectively reduce processing viscosity, improve aging resistance, and inhibit the precipitation of small molecules, thus meeting the stringent requirements of high-end equipment manufacturing for thermal interface materials.

[0076] In summary, the alkoxy anchoring agent provided by this invention has a unique molecular structure design. The side-chain phenyl group enhances thermal stability, the side-chain butyl group improves flexibility and wettability, the terminal alkoxy group achieves powder anchoring, and the side-chain silane participates in the construction of the cross-linking network. The thermally conductive pad composite material prepared using the alkoxy anchoring agent of this invention exhibits low processing viscosity, excellent aging resistance, and low small molecule exudation rate, meeting the requirements of demanding applications such as optical modules.

[0077] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An alkoxy anchoring agent for thermally conductive powder, characterized in that, Its molecular structure is as follows: R-(MeHSiO) a (Me2SiO) x (MePhSiO) b (MeBuSiO) c -Si(CH2)3Si(OCH3)3; Wherein, R is one of butyl, octyl, and dodecyl, a is a natural number from 1 to 4, x is a natural number from 12 to 46, b is a natural number from 1 to 5, and c is a natural number from 1 to 5.

2. A synthesis process for an alkoxy anchoring agent for thermally conductive powder as described in claim 1, characterized in that, Includes the following steps: S1. Under inert gas protection, dissolve alkyl dimethylchlorosilane in dry toluene, cool to 0-6℃, add tetramethylammonium hydroxide solution dropwise, and after the reaction, allow it to naturally warm to room temperature while stirring. S2. Add methyl hydrogen cyclosiloxane and stir at room temperature to allow it to undergo ring-opening polymerization, thereby obtaining a short-chain polymer with active ends and silane close to the octyl group. S3. Add the dried monomer mixture and heat to 75-95℃ with stirring to react; the monomer mixture is a mixture of octamethylcyclotetrasiloxane, methylphenylcyclosiloxane and methylbutylcyclosiloxane; S4. After cooling to room temperature, add allyl dimethylchlorosilane, stir, and reflux. S5. Add acetic acid to neutralize the tetramethylammonium hydroxide alcohol solution, filter, and distill under reduced pressure to obtain the terminal allyl silicone oil intermediate. S6. The terminal allyl silicone oil intermediate is subjected to a hydrosilylation reaction with trimethoxysilane in the presence of a platinum catalyst. S7. Add activated carbon for adsorption and filtration, and remove excess trimethoxysilane by vacuum distillation to obtain alkoxy anchoring agent.

3. The synthesis process of the alkoxy anchoring agent for thermally conductive powder as described in claim 2, characterized in that, The molar proportions of each raw material are based on the amount of alkyl dimethylchlorosilane used as 1 part: The amount of the methyl hydrogen cyclosiloxane used is 0.5-0.85 parts; The amount of the octamethylcyclotetrasiloxane used is 4-6 parts; The amount of the methylphenylcyclosiloxane used is 0.11-0.18 parts; The amount of the methylbutylcyclosiloxane used is 0.1-0.15 parts; The amount of allyl dimethylchlorosilane used is 1.1-1.2 parts; The amount of the trimethoxysilane used is 1.21-1.32 parts; The amount of the tetramethylammonium hydroxide alcohol solution used is 0.9-1.0 parts; The amount of acetic acid used is 0.02-0.05 parts; The amount of dried toluene used is 3-5 parts.

4. The synthesis process of the alkoxy anchoring agent for thermally conductive powder as described in claim 2, characterized in that, In step S2, the methyl hydrogen cyclosiloxane is selected from one of methyl hydrogen cyclotrisiloxane and methyl hydrogen cyclotetrasiloxane.

5. The synthesis process of the alkoxy anchoring agent for thermally conductive powder as described in claim 2, characterized in that, In step S3, the methylbutylcyclosiloxane is selected from one of methylbutylcyclotrisiloxane and methylbutylcyclotetrasiloxane; the methylphenylcyclosiloxane is selected from one of methylphenylcyclotrisiloxane and methylphenylcyclotetrasiloxane.

6. The synthesis process of the alkoxy anchoring agent for thermally conductive powder as described in claim 2, characterized in that, In step S3, the tetramethylammonium hydroxide alcohol solution is a methanol solution with a tetramethylammonium hydroxide concentration of 20%-25%.

7. The synthesis process of the alkoxy anchoring agent for thermally conductive powder as described in claim 2, characterized in that, In step S6, the platinum catalyst is a caster platinum catalyst or a chloroplatinic acid catalyst, and the platinum content is 1-5 ppm.

8. The application of an alkoxy anchoring agent for thermally conductive powder as described in claim 1 in the preparation of thermally conductive composite materials.

9. The application of the alkoxy anchoring agent for thermally conductive powder as described in claim 8 in the preparation of thermally conductive composite materials, characterized in that, The thermally conductive composite material is either a thermally conductive pad composite material or a thermally conductive gel composite material.

10. A thermally conductive pad composite material, characterized in that, It is prepared from the following parts by weight of raw materials: 100 parts of vinyl-terminated silicone oil; Hydrogen-containing silicone oil 0.4-3 parts; Polymerization inhibitor 0.01-0.06 parts; Pigment 0.2-0.6 parts; Catalyst 0.1-0.5 parts; 0.6-2.2 parts of the alkoxy anchoring agent as described in claim 1; 18-25 parts of thermally conductive powder filler; The thermally conductive powder filler is a mixture of spherical alumina, spherical alumina and spherical aluminum nitride powder.

Images