Secondary surface modification method of inorganic heat-conducting powder and application thereof

Abstract

The invention relates to a secondary surface modification method of inorganic heat-conducting powder and application of the inorganic heat-conducting powder. The method adopts a step-by-step modification process and comprises the following steps: firstly, mixing 100 parts of inorganic powder and 0.1-0.9 part of a self-developed ester-terminated macromolecular silane coupling agent (taking a Si-O chain as a main chain with one end terminated by an ester group and the other end terminated by an alkoxy group) for 1-10 minutes at 500-1200 rpm for pre-modification; and then adding 0.2-1.0 part of a short-chain silane coupling agent with the carbon chain length of less than 8, and mixing for 1-10 minutes for secondary modification. The secondary surface modification method disclosed by the invention has a synergistic effect, the self-developed ester-terminated macromolecular silane coupling agent is anchored with hydroxyl on the surface of the powder firstly, and then short-chain silane is used for further optimizing the interface performance of the powder, so that the viscosity of the system is remarkably reduced, and the thixotropic problem caused by single use of macromolecular silane is avoided; the thermal interface material prepared from the inorganic powder subjected to secondary surface modification has excellent high temperature resistance, hydrolysis resistance, sedimentation resistance and constructability.

Description

Technical Field

[0001] The present invention belongs to the technical field of inorganic powder surface modification and relates to a method for secondary surface modification of inorganic thermally conductive powders and its application. Specifically, it relates to a method for secondary surface modification of inorganic powders using a macromolecular silane coupling agent with a Si-O chain as the main chain, an ester endcapping at one end, and an alkoxy endcapping at the other end, in conjunction with a short-chain silane coupling agent, acting in a specific sequence to synergistically modify the surface of the inorganic powder. Background Art

[0002] Thermally conductive powders are widely used in electronics, energy, and high-performance composite materials, particularly in thermal management and heat dissipation materials. The thermal conductivity, dispersibility, and stability of the powder are crucial to the performance of the final product. To enhance the performance of powders, existing technologies commonly use silane coupling agents for surface chemical modification.

[0003] Silane coupling agents can chemically react with the surface of inorganic powders through their silicon-oxygen bonds, forming a stable surface layer, improving the powder's dispersibility and matrix compatibility, and further improving the powder's thermal conductivity. Existing common modification methods mainly rely on a single type of short-chain, long-chain, or macromolecular silane coupling agent to treat the powder surface. For example, short-chain silane coupling agents (such as KH-550 and KH-560) can bond with the powder surface through silanol groups to improve dispersibility, but their short molecular chains and low steric hindrance make it difficult to form a stable coating. While long-chain and macromolecular silane coupling agents can enhance interfacial bonding strength, they may cause powder agglomeration due to their excessively long molecular chains, which in turn reduces dispersion uniformity. Therefore, modification with a single type of silane coupling agent makes it difficult to achieve a synergistic improvement in thermal conductivity, dispersibility, and thermal stability.

[0004] In order to overcome this problem, recent studies have proposed a secondary modification technology, that is, to optimize surface properties by sequential treatment of two coupling agents. For example, CN117757286A discloses an alkali-resistant spherical silica slurry for packaging substrates and a preparation method thereof, wherein the method first compounded submicron spherical silica and micron spherical silica, and then used a silane coupling agent to wet-modify the compounded spherical silica, and then used a non-polar short-chain silane coupling agent for secondary modification, and finally the modified silica was dispersed in an organic solvent, and spherical silica slurry was obtained by classification; however, these technologies still have problems such as complex process, uneven modification effect, and poor thermal stability during the modification process. Therefore, how to achieve the synergistic optimization of thermal conductivity, dispersibility and thermal stability while simplifying the process through the innovative design of coupling agent type and modification sequence has become a difficult problem to be solved in the current technology.

[0005] The present invention proposes a new secondary modification method, which utilizes a combination of a self-developed ester-terminated macromolecular silane coupling agent and a short-chain silane coupling agent to perform surface treatment on inorganic powders according to a specific modification sequence, thereby significantly improving the interfacial compatibility and dispersibility between the inorganic powders and the organic matrix, and the modification effect is long-lasting and stable. Summary of the Invention

[0006] The present invention proposes a method for secondary surface modification of inorganic thermal conductive powder and its application. The preparation method of the present invention uses a combination of a self-developed ester-terminated macromolecular silane coupling agent and a short-chain silane coupling agent to perform secondary modification on the surface of the inorganic powder in a specific modification order. The self-developed ester-terminated macromolecular silane coupling agent has a Si-O chain as the main chain, an ester end-capping end, and an alkoxy end-capping end, and has excellent heat resistance and anti-settling properties. In the secondary modification process, a macromolecular silane coupling agent is first used for pre-modification, and then a short-chain silane coupling agent is used for subsequent secondary modification. The modification method of the present invention can effectively improve the dispersibility, heat resistance and stability of the inorganic powder, effectively enhance the interfacial bonding force between the powder and the matrix material, and solve the problems of poor compatibility, uneven dispersion, poor temperature resistance, poor stability, etc. when inorganic powder is used in high-performance thermal conductive materials in the prior art.

[0007] To achieve the above-mentioned object, the present invention provides a method for secondary surface modification of an inorganic thermally conductive powder. The modification method comprises the following steps: taking 100 parts of inorganic powder and placing it in a high-speed disperser with a stirring paddle, adding 0.1-0.9 parts of a self-developed ester-terminated macromolecular silane coupling agent, and mixing at a speed of 500-1200 rpm for 1-10 minutes for preliminary modification; then adding 0.2-1.0 parts of a short-chain silane coupling agent and mixing for 1-10 minutes for secondary modification, and finally obtaining a powder that is a secondary modified inorganic thermally conductive powder; the self-developed ester-terminated macromolecular silane coupling agent has a Si-O chain as the main chain, an ester end capped at one end, and an alkoxy end capped at the other end; and the carbon chain length of the short-chain silane coupling agent is less than 8.

[0008] The inorganic thermal conductive powder is one or more of aluminum oxide, magnesium oxide, zinc oxide, silicon dioxide, titanium dioxide, aluminum hydroxide, boron nitride, and aluminum nitride.

[0009] The short-chain silane coupling agent has a carbon chain length of less than 8 and is specifically one of aminosilane, sulfur-containing silane, epoxysilane or methacryloxysilane.

[0010] The added amount of the self-developed ester-terminated macromolecular silane coupling agent is less than that of the short-chain silane coupling agent, and the total added amount does not exceed 2% of the powder mass.

[0011] The method for preparing the self-developed ester-terminated macromolecular silane coupling agent comprises the following steps: a. Mixing terminal hydrogenated silicone oil with a solvent under nitrogen to obtain a mixed solution; adding a catalyst to the mixed solution and heating it, adding vinyl alkoxysilane at 70-80° C., controlling the dropwise addition rate to 1 d / s, and reacting at 80-90° C. for 2-16 hours after the dropwise addition is completed; after the reaction is completed, the crude product is subjected to reduced pressure distillation at 0.01-0.1 MPa to remove low-boiling fractions to obtain an intermediate product; b. At room temperature, mixing the obtained intermediate product with a solvent, adding a catalyst, introducing nitrogen protection, heating the system to 70-80° C., adding acrylate at this temperature, controlling the dropwise addition rate to 1 d / s, and reacting at 80-90° C. for 2-16 hours after the dropwise addition is completed; after the reaction is completed, the crude product is subjected to reduced pressure distillation at 0.01-0.1 MPa to remove low-boiling fractions to obtain an ester-terminated macromolecular silane coupling agent having a structure shown in general formula (1): Wherein R in the general formula (1) is one of an alkyl group and an aryl group; R1 is -CH3, -CH2CH3, -(CHCH3)2, -COCH3; R2 and R3 are one of -OCH3, -OCH2CH3, -O(CHCH3)2, -OCOCH3, -CH3, -CH2CH3, -(CHCH3)2; n is a natural number of 10-100; The chemical reaction formulas in steps a and b are as follows: a. Reaction formula for intermediate generation b. Reaction formula for the final product

[0012] The viscosity of the hydrogen-terminated silicone oil in step a is 20 to 10,000 mPa﹒s, and has the structure shown in general formula (2): Wherein, n in the general formula (2) is a natural number from 10 to 100.

[0013] The vinyl alkoxysilane in step a is one of vinyl monoalkoxysilane, vinyl dialkoxysilane or vinyl trialkoxysilane, and has a structure shown in general formula (3): In the general formula (3), R1 is one of -CH3, -CH2CH3, -(CHCH3)2, and -COCH3; R2 and R3 are one of -OCH3, -OCH2CH3, -O(CHCH3)2, -OCOCH3, -CH3, -CH2CH3, and -(CHCH3)2.

[0014] The acrylate in step b has a structure shown in general formula (4): In the general formula (4), R is an alkyl group or an aryl group.

[0015] The solvents in steps a and b are one or more of toluene, dichloromethane, chloroform or n-hexane; and the catalysts are one of Karstedt catalyst and Wilkinson catalyst.

[0016] The amount of the catalyst added in step a is 0.1%-5% of the terminal hydrogen silicone oil; the molar ratio of the terminal hydrogen silicone oil to vinyl alkoxysilane is 1:0.2-0.5; and the amount of the solvent added is 0.5-1.5 ml of solvent per 1 g of terminal hydrogen silicone oil.

[0017] In step b, the amount of the catalyst added is 0.1%-5% of the intermediate product; the molar ratio of the intermediate product to the acrylate is 0.5-2:1; and the amount of the solvent added is 0.5-1.5 ml of solvent per 1 g of the intermediate product.

[0018] The inorganic thermally conductive powder that has undergone secondary surface modification is used to prepare thermal interface thermally conductive materials, including thermally conductive gaskets, thermally conductive gels, thermally conductive potting glue, thermally conductive silicone grease, and thermally conductive mud.

[0019] It is worth noting that the modification sequence of the secondary surface modification method of the inorganic thermal conductive powder of the present invention is fixed. It is necessary to first add a self-developed ester-terminated macromolecular silane coupling agent for pre-modification, and then add a short-chain silane coupling agent to mix for secondary modification; the self-developed ester-terminated macromolecular silane coupling agent pre-modification can form stable Si-O bonds on the powder surface, and the subsequent secondary modification further optimizes the powder interface performance. This fixed sequence can significantly improve the dispersibility of the powder and its compatibility with the matrix. If the modification sequence is changed and the short-chain silane coupling agent is used for surface treatment first, the powder surface will be linked to too many small molecules, which is not conducive to the subsequent linking of the self-developed ester-terminated macromolecular silane coupling agent with the powder, resulting in a reduced effect of improving the compatibility between the powder and the matrix, and thus failing to achieve the modification effect of the present invention.

[0020] The beneficial effects of the present invention are as follows: (1) The inorganic thermally conductive powder prepared by the present invention has excellent thermal stability, and the thermal interface materials such as thermal conductive gaskets / gels prepared therefrom have excellent temperature resistance and low volatility. The ester-terminated macromolecular silane coupling agent molecules developed by the present invention have a Si-O main chain structure and are highly thermally stable. The bond energy of the Si-O bond (about 460kJ / mol) is much higher than that of organic bonds such as CC (about 332kJ / mol) or CO (about 336kJ / mol). The excellent structural stability makes it difficult to decompose in a high-temperature environment, so the thermal interface material finally prepared also has excellent heat resistance. (2) The inorganic thermal conductive powder prepared by the present invention has excellent storage stability. The ester group in the molecular structure of the self-developed ester-terminated macromolecular silane coupling agent has high chemical stability and exhibits excellent hydrolysis stability under conventional storage conditions, significantly improving the storage performance of the product; in addition, the ester group can form a three-dimensional network structure through orientation force, maintain a high viscosity under static or low shear conditions to effectively prevent the filler from settling, and under high shear, the network structure can reversibly dissociate, so that the viscosity of the system decreases and the fluidity is restored to facilitate construction. It is worth noting that the ester group contained in the structure of the present invention is a terminal ester, which can undergo controllable hydrolysis to generate a carboxyl group under extreme conditions such as acid-base catalysis or heating. The carboxyl group can be linked to the inorganic filler or substrate through chemical bonds or physical adsorption, which is beneficial to improving the dispersion between fillers in the composite material and its adhesion to the matrix. (3) The inorganic thermal conductive powder prepared by the present invention has good compatibility with the resin matrix. The siloxane group (Si-OR) in the molecular structure of the self-developed ester-terminated macromolecular silane coupling agent can be hydrolyzed to generate a highly reactive silanol group (Si-OH), which undergoes a condensation reaction with the abundant hydroxyl groups (-OH) on the surface of the inorganic powder to form a stable Si-O-Si covalent bonding interface, thereby achieving chemical anchoring of the coupling agent molecules on the surface of the inorganic filler and improving the compatibility of the inorganic thermal conductive powder with the resin matrix. Secondly, the step-by-step secondary modification process of the ester-terminated macromolecular silane coupling agent and the short-chain silane coupling agent has a synergistic effect; the ester-terminated macromolecular silane coupling agent is prone to thixotropy or high viscosity due to its large molecular weight, and the high stability of the large molecular weight may cause incomplete modification and coating of the powder; at this time, the introduction of the short-chain silane coupling agent for secondary modification effectively increases the surface coating rate of the powder, improves the dispersibility of the powder, and achieves an excellent viscosity reduction effect. DETAILED DESCRIPTION

[0021] The following embodiments are merely illustrative of the technical solutions of the present invention and are not intended to limit the scope of the present invention. Those skilled in the art should understand that, without departing from the essential features and design concepts of the technical solutions of the present invention, any modification, equivalent replacement or improvement of the technical solutions described in the aforementioned embodiments should be included within the scope of protection of the claims of the present invention.

[0022] Example 1 (1) Preparation of ester-terminated macromolecular silane coupling agent ① Add 75 mL of anhydrous toluene to a 250 mL dry three-necked flask. After nitrogen protection, add 50 g of 20 cps hydrogen-terminated silicone oil and mix thoroughly to obtain a mixed solution. Add 0.1 g of Karstedt catalyst to this solution. Raise the temperature to 70°C and slowly add 2.70 g of vinyltrimethoxysilane dropwise at this temperature. After the addition is complete, continue stirring at 80°C for 8 hours. After the reaction is complete, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1 MPa to obtain the intermediate product. ② At room temperature, add 25g of the intermediate product obtained in step 1 and 30mL of anhydrous toluene to a 150mL dry three-necked flask. Mix thoroughly, then add 0.1g of Karstedt catalyst. After nitrogen protection, slowly add 1.72g of methyl acrylate dropwise at 70°C. After the addition is complete, continue stirring at 80°C for 8h. After the reaction is complete, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1MPa to obtain the target macromolecular silane coupling agent. (2) Secondary surface modification of inorganic thermal conductive powder: The inorganic thermal conductive powder formula is: 10% 1μm (the powder particle size described below is the median diameter D50) zinc oxide, 10% 1μm spherical alumina, 20% 5μm spherical alumina, 20% 40μm spherical alumina, and 40% 70μm spherical alumina. 3 kg of the mixed inorganic thermal conductive powder was placed in a high-speed disperser with a stirring paddle (rotating speed of 1200 rpm), and 0.3% of the ester-terminated macromolecular silane coupling agent prepared in (1) was added and mixed together for 2 minutes; after the addition, 0.7% of KH-550 silane coupling agent was added and mixed again for 2 minutes. The final powder obtained was the secondary modified inorganic thermal conductive powder.

[0023] Example 2 (1) Preparation of ester-terminated macromolecular silane coupling agent ① Add 50 mL of dichloromethane to a 250 mL dry three-necked flask. After nitrogen protection, add 50 g of 100 cps end-hydrogenated silicone oil and stir to obtain a mixed solution. Add 0.12 g of Wilkinson catalyst to this mixed solution. Raise the temperature to 80°C and slowly add 0.42 g of vinyltriethoxysilane dropwise at this temperature. After the addition is complete, continue stirring at 90°C for 6 hours. After the reaction is complete, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1 MPa to obtain the intermediate product. ② At room temperature, add 25g of the intermediate product obtained in step 1 and 20mL of dichloromethane to a 150mL dry three-necked flask. After mixing thoroughly, add 0.12g of Wilkinson catalyst. After nitrogen protection, slowly add 0.67g of ethyl acrylate dropwise at 80°C. After the addition is complete, continue stirring at 90°C for 6h. After the reaction is complete, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1MPa to obtain the target macromolecular silane coupling agent. (2) Secondary surface modification of inorganic thermal conductive powder: The formula of the inorganic thermal conductive powder is the same as that in Example 1. Secondary modification method: take 3 kg of the mixed inorganic thermal conductive powder mentioned above and place it in a high-speed disperser with a stirring paddle (rotation speed is 900 rpm), add 0.2% of the ester-terminated macromolecular silane coupling agent prepared in (1), and mix together for 5 minutes; after the end, add 0.5% of KH-560 silane coupling agent and mix again for 3 minutes. The final powder obtained is the secondary modified inorganic thermal conductive powder.

[0024] Example 3 (1) Preparation of ester-terminated macromolecular silane coupling agent ① Add 40 mL of n-hexane to a 250 mL dry three-necked flask. After nitrogen protection, add 50 g of 250 cps hydrogen-terminated silicone oil and stir to obtain a mixed solution. Add 0.15 g of Wilkinson catalyst to this mixed solution. Raise the temperature to 80°C and slowly add 0.25 g of vinylmethyldimethoxysilane dropwise at this temperature. After the addition is complete, continue stirring at 90°C for 10 hours. After the reaction is complete, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1 MPa to obtain the intermediate product. ② At room temperature, add 25g of the intermediate product obtained in step 1 and 35mL of n-hexane to a 150mL dry three-necked flask. After mixing thoroughly, add 0.15g of Karstedt catalyst. After nitrogen protection, slowly add 0.23g of propyl acrylate dropwise at 80°C. After the addition is complete, continue stirring at 90°C for 10 hours. After the reaction is complete, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1MPa to obtain the target macromolecular silane coupling agent. (2) Secondary surface modification of inorganic thermal conductive powder: The formula of the inorganic thermal conductive powder is the same as that in Example 1. Secondary modification method: 3 kg of the mixed inorganic thermal conductive powder was placed in a high-speed disperser with a stirring paddle (rotation speed of 1000 rpm), and 0.3% of the ester-terminated macromolecular silane coupling agent prepared in (1) was added and mixed together for 8 minutes; after the end, 0.4% of KH-570 silane coupling agent was added and mixed again for 5 minutes. The final powder obtained was the secondary modified inorganic thermal conductive powder.

[0025] Example 4 (1) Preparation of ester-terminated macromolecular silane coupling agent ① Add 50 mL of chloroform to a 250 mL dry three-necked flask, purge with nitrogen, and then add 100 g of 500 cps end-hydrogenated silicone oil. Stir evenly to obtain a mixed solution. Add 1.0 g of Wilkinson catalyst to the mixed solution, raise the temperature to 70°C, and slowly dropwise add 0.37 g of vinyldimethylethoxysilane at this temperature. Continue stirring at 90°C for 4 hours. After the reaction is completed, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1 MPa to obtain an intermediate product. ② At room temperature, add 25g of the intermediate product obtained in step 1 and 30mL of chloroform to a 150mL dry three-necked flask. After mixing thoroughly, add 1.0g of Wilkinson catalyst. Under nitrogen protection, slowly add 0.17g of butyl acrylate dropwise at 70°C. After the addition is complete, continue stirring at 90°C for 4h. After the reaction is complete, cool to room temperature and remove low-boiling fractions by vacuum distillation at 0.01-0.1MPa to obtain the target macromolecular silane coupling agent. (2) Secondary surface modification of inorganic thermal conductive powder: The formula of the inorganic thermal conductive powder is the same as that in Example 1. Secondary modification method: take 3 kg of the mixed inorganic thermal conductive powder mentioned above and place it in a high-speed disperser with a stirring paddle (rotation speed is 800 rpm), add 0.1% of the ester-terminated macromolecular silane coupling agent prepared in (1), and mix them together for 10 minutes; after the end, add 0.5% of KH-590 silane coupling agent and mix again for 2 minutes. The final powder obtained is the secondary modified inorganic thermal conductive powder.

[0026] Example 5 The preparation steps and dosage of the ester-terminated macromolecular silane coupling agent are the same as those in Example 1; the method and dosage of the secondary surface modification of the inorganic thermally conductive powder are the same as those in Example 1; only the formula of the inorganic thermally conductive powder is changed. The formula of the inorganic thermally conductive powder in Example 5 is: 15% 1 μm (the powder particle size described below is the median diameter D50) zinc oxide, 10% 5 μm single crystal spherical aluminum nitride, 25% 5 μm spherical aluminum oxide, 20% 20 μm zinc oxide, and 30% 70 μm polycrystalline spherical aluminum nitride.

[0027] To demonstrate the specific application effects of the above examples, a thermally conductive silicone composition, a thermally conductive gasket, and a thermally conductive epoxy composition were prepared using the secondary modified inorganic thermally conductive powders of Examples 1-5. The thermally conductive silicone composition and thermally conductive gasket were tested for parameters such as settling distance, viscosity, thermal conductivity, and mechanical properties, allowing for comparison and analysis.

[0028] Application Examples 1-5 Preparation of a thermally conductive silicone composition: The secondary modified inorganic thermally conductive powder prepared in Examples 1-5 and 500 cP vinyl silicone oil were added to a high-speed mixer (at a speed of 900 rpm) in a mass ratio of 18:1 and mixed for 30 minutes to obtain a thermally conductive silicone composition; the thermally conductive silicone compositions prepared in Examples 1-5 correspond to Application Examples 1-5.

[0029] Application Examples 6-10 Preparation of thermally conductive gaskets: Mix 2300 parts of the secondary modified inorganic thermally conductive powder prepared in Examples 1-5, 100 parts of 500cP vinyl silicone oil, 3 parts of hydrogenated silicone oil, 0.3 parts of 3000ppm platinum catalyst, and 0.3 parts of inhibitor, press into a thickness of 2mm, and cure at 120°C for 15 minutes to make 6W thermally conductive gaskets; the thermally conductive gaskets prepared in Examples 1-5 correspond to Application Examples 6-10.

[0030] Application Examples 11-15 Thermally conductive epoxy composition: 50 parts of the secondary modified inorganic thermally conductive powder prepared in Examples 1-5, 100 parts of 1000cp bisphenol A epoxy resin, and 10 parts of an amine curing agent were mixed uniformly, and then vacuum degassing (900r, 2min) was performed to obtain a thermally conductive epoxy composition; the thermally conductive epoxy compositions prepared in Examples 1-5 correspond to Application Examples 11-15.

[0031] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the secondarily modified inorganic thermally conductive powder of Example 1 is replaced with untreated inorganic powder; the formula of the inorganic thermally conductive powder of Comparative Example 1 is the same as that of the inorganic thermally conductive powder of Example 1.

[0032] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that the inorganic thermally conductive powder formula is to replace the inorganic thermally conductive powder secondarily modified in Example 1 with an inorganic powder modified with the ester-terminated macromolecular silane coupling agent prepared in Example 1 alone. The specific method for modifying the inorganic powder used in Comparative Example 2 is: Inorganic thermal conductive powder formula: 10% 1μm D50 zinc oxide, 10% 1μm spherical alumina, 20% 5μm spherical alumina, 20% 40μm spherical alumina, 40% 70μm spherical alumina. 3 kg of the mixed inorganic thermal conductive powder was placed in a high-speed disperser with a stirring blade (rotation speed of 1200 rpm), and 0.9% of the ester-terminated macromolecular silane coupling agent prepared in (1) was added and mixed for 4 minutes to obtain the modified inorganic thermal conductive powder of Comparative Example 2.

[0033] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the inorganic thermally conductive powder modified twice in Example 1 is replaced by inorganic powder modified solely with commercially available KH-550 silane coupling agent. The specific method for modifying the inorganic powder used in Comparative Example 3 is: Inorganic thermal conductive powder formula: 10% 1μm D50 zinc oxide, 10% 1μm spherical alumina, 20% 5μm spherical alumina, 20% 40μm spherical alumina, 40% 70μm spherical alumina. 3 kg of the mixed inorganic thermally conductive powder was placed in a high-speed disperser with a stirring blade (rotation speed of 1200 rpm), and 1.0% KH-550 silane coupling agent was added and mixed for 4 minutes to obtain the modified inorganic thermally conductive powder of Comparative Example 3.

[0034] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the inorganic thermally conductive powder modified twice in Example 1 is replaced by an inorganic powder modified first with a commercially available KH-550 silane coupling agent and then with the ester-terminated macromolecular silane coupling agent prepared in Example 1. The specific method for modifying the inorganic powder used in Comparative Example 4 is as follows: Inorganic thermal conductive powder formula: 10% 1μm D50 zinc oxide, 10% 1μm spherical alumina, 20% 5μm spherical alumina, 20% 40μm spherical alumina, 40% 70μm spherical alumina. 3 kg of the mixed inorganic thermal conductive powder was placed in a high-speed disperser with a stirring paddle (rotating speed of 1200 rpm), 0.7% KH-550 silane coupling agent was added, and the mixture was mixed for 2 minutes. After the mixture was mixed, 0.3% of the ester-terminated macromolecular silane coupling agent prepared in (1) was added and the mixture was mixed for another 2 minutes to obtain the inorganic thermal conductive powder used in Example 4.

[0035] Comparative Application Examples 1-4 Comparative Application Examples 1-4: The inorganic powder or modified inorganic powder used in Comparative Examples 1-4 is used to prepare a thermally conductive silicone composition according to the method and dosage of Application Example 1. Comparative Application Example 1 corresponds to a thermally conductive silicone composition prepared using the inorganic powder used in Comparative Example 1; Comparative Application Example 2 corresponds to a thermally conductive silicone composition prepared using the inorganic powder used in Comparative Example 2; Comparative Application Example 3 corresponds to a thermally conductive silicone composition prepared using the inorganic powder used in Comparative Example 3; and Comparative Application Example 4 corresponds to a thermally conductive silicone composition prepared using the inorganic powder used in Comparative Example 4.

[0036] Comparative Application Examples 5-8 In comparative application examples 5-8, the inorganic powder or modified inorganic powder used in comparative examples 1-4 is used to prepare thermally conductive gaskets according to the method and dosage of application example 6. Comparative application example 5 corresponds to a thermally conductive gasket prepared with the inorganic powder used in comparative example 1; comparative application example 6 corresponds to a thermally conductive gasket prepared with the inorganic powder used in comparative example 2; comparative application example 7 corresponds to a thermally conductive gasket prepared with the inorganic powder used in comparative example 3; comparative application example 8 corresponds to a thermally conductive gasket prepared with the inorganic powder used in comparative example 4.

[0037] Comparative Application Examples 9-12 In comparative application examples 9-12, the inorganic powder or modified inorganic powder used in comparative examples 1-4 is used to prepare a thermally conductive epoxy composition according to the method and dosage of application example 11. Comparative application example 9 corresponds to a thermally conductive epoxy composition prepared using the inorganic powder used in comparative example 1; comparative application example 10 corresponds to a thermally conductive epoxy composition prepared using the inorganic powder used in comparative example 2; comparative application example 11 corresponds to a thermally conductive epoxy composition prepared using the inorganic powder used in comparative example 3; comparative application example 12 corresponds to a thermally conductive epoxy composition prepared using the inorganic powder used in comparative application example 4.

[0038] Performance Testing Various performance tests were conducted for the corresponding use cases and comparison ratios, and the test data are shown in Table 1, Table 2, Table 3, Table 4, and Table 5. The performance test method is as follows: Volatile Matter Test: Weigh 50g of the inorganic thermally conductive powder or modified thermally conductive powder from Examples 1-5 and Comparative Examples 1-4, dry them in an oven at 150±2°C for 12 hours, then transfer them to a glass desiccator and cool them. After cooling to room temperature, weigh the dried sample and calculate the amount of volatile additive released. See Table 1 for detailed test results. Hydrolysis Resistance Test: 50g of the inorganic thermally conductive powders or modified thermally conductive powders from Examples 1-5 and Comparative Examples 1-4 were soaked in deionized water at 60°C for 24, 48, and 72 hours, respectively. The samples were then filtered, dried at 60°C to constant weight, and transferred to a desiccator for cooling to room temperature. After cooling to room temperature, the dried samples were weighed and their mass loss was calculated. The test results are detailed in Table 1. Sedimentation performance was tested by placing 80 mL of each of the thermally conductive silicone compositions prepared in Application Examples 1-5 and Comparative Application Examples 1-4 into a 100 mL graduated cylinder. The mixture was allowed to stand in a cool, ventilated place for 120 days. The height of the supernatant was measured on the 30th, 60th, and 120th day. The height of the supernatant (i.e., the distance separating the oil and powder) and the presence of hard agglomerates were used as indicators of sedimentation performance. The results are shown in Table 2. Viscosity test: The thermally conductive silicone compositions prepared in Application Examples 1-5 and Comparative Application Examples 1-4 were placed in transparent gel cups, and the viscosity of the gels was tested using an NDJ-8S digital rotational viscometer. The viscosity values ​​were measured at 6 r / min, 30 r / min, and 50 r / min, respectively. The viscosity value was used as an indicator of the compatibility of the powder with the silicone. The results are shown in Table 3. Thermal conductivity test: The thermal conductivity coefficient of the thermally conductive gaskets prepared in Application Examples 6-10 and Comparative Application Examples 5-8 was tested using a DRL-Ⅲ thermal conductivity meter. The sample diameter was 20 mm, the thickness was 2 mm, and the test pressure was 30 N. The results are shown in Table 4. Mechanical properties test: A tensile testing machine (Zwick Z010) was used to test the tensile strength and elongation at break of the thermal pads prepared in Application Examples 6-10 and Comparative Application Examples 5-8. The tensile strength and elongation at break were in accordance with GB / T 528-1998. The results are shown in Table 4. Bond Shear Strength Testing: The thermally conductive epoxy compositions prepared in Examples 11-15 were compared with those prepared in Examples 11-12. Using a standard aluminum sheet (25 mm x 100 mm) as the substrate, the adhesive was evenly applied to the overlap area (12.5 mm x 25 mm). The two aluminum sheets were overlapped and clamped. After initial curing at room temperature for 4 hours and heat curing at 80°C for 2 hours, tensile shear testing was performed using a computer servo dual-column tensile testing machine to evaluate the enhanced interfacial bonding performance of the modified inorganic powder in the resin system, particularly the enhanced bond strength achieved by the modified coupling agent of the present invention. The results are shown in Table 5. Table 1 Volatile matter and mass loss of thermal conductive powders or modified thermal conductive powders prepared in Examples 1-5 and Comparative Examples 1-4 As shown in Table 1, compared to Comparative Examples 1-4, the inorganic powders modified in Examples 1-5, which include the coupling agent developed by the present invention and secondary modification, exhibit the best hydrolysis resistance and thermal stability. Unmodified powders and Comparative Examples 1-3, which use only one treatment agent, lack or are incompletely coated with an organic protective layer on their surfaces, exposing hydrolysis-sensitive sites. These sites are susceptible to reaction with water molecules or structural loosening in hot and humid environments, leading to partial particle loss or agglomeration and sedimentation that makes complete drying difficult. This ultimately results in a significant mass loss rate, resulting in poor surface stability and making it difficult to meet the requirements of high-reliability applications. Table 2 Sedimentation properties of thermally conductive silicone compositions prepared in Application Examples 1-5 and Comparative Application Examples 1-4 Group 30 days 60 days 120 days Whether it is lumpy Application Example 1 0 1 3 no Application Example 2 0 2 5 no Application Example 3 0 2 3 no Application Example 4 0 3 5 no Application Example 5 0 1 4 no Comparative Application Example 1 15 28 35 yes Comparative Application Example 2 5 12 19 yes Comparative Application Example 3 10 21 29 yes Comparative Application Example 4 6 11 19 yes As shown in Table 2, compared to Comparative Examples 1-4, the thermally conductive silicone compositions prepared using the secondary modified thermally conductive powders prepared in Examples 1-5 of the present invention exhibited virtually no delamination after prolonged storage, exhibited low supernatant heights, and exhibited no soft or hard lumps at the bottom of the colloid. This demonstrates that the ester-terminated macromolecular silane coupling agent of the present invention synergizes with the short-chain silane coupling agent to achieve excellent anti-settling properties. Table 3 Viscosity performance test of thermally conductive silicone compositions prepared in Application Examples 1-5 and Comparative Application Examples 1-4 As shown in Table 3, compared to Comparative Examples 1-4, the viscosity of the thermally conductive silicone compositions in Examples 1-5, prepared using the secondary modified thermally conductive powders prepared in accordance with the present invention, is lower. This indicates that, after secondary modification in a specific order using the ester-terminated macromolecular silane coupling agent and the short-chain silane coupling agent prepared in accordance with the present invention, Examples 1-5 exhibit improved oil solubility and are more easily dispersed in silicone oil. Furthermore, the viscosity values ​​at different rotational speeds indicate that as the rotational speed increases, Examples 1-5 exhibit a thixotropic effect, indicating that increased shear forces facilitate the transition of the thermally conductive silicone compositions from a viscous state to a fluid state, achieving a similar "thixotropic" effect. Table 4 Thermal conductivity and mechanical properties test of thermal conductive pads prepared in Application Examples 6-10 and Comparative Application Examples 5-8 As can be seen from Table 4, compared with comparative application examples 5-8, thermal conductive gasket application examples 6-10 prepared using the secondary modified thermal conductive powder prepared in the embodiments of the present invention showed certain improvements in thermal conductivity, tensile strength and elongation at break. Table 5 Thermal conductivity and mechanical properties of the thermally conductive epoxy compositions prepared in Application Examples 11-15 and Comparative Application Examples 9-12 As shown in Table 5, compared to Comparative Examples 9-12, the thermally conductive gaskets prepared in Examples 11-15 of the present invention exhibited the best interfacial bonding performance, with shear strength increased by over 80% compared to the untreated group, with most manifestations being substrate damage, indicating strong interfacial bonding and high structural integrity. Overall, the ester-terminated macromolecular silane coupling agent prepared in the present invention, when used in conjunction with a short-chain silane coupling agent, significantly enhanced the bonding strength of silica powder in the resin, demonstrating excellent interfacial activity and structural stability. In summary, the ester-terminated macromolecular silane coupling agent and the short-chain silane coupling agent prepared by the present invention adopt a step-by-step modification process, showing a significant synergistic effect. First, the inorganic filler is surface pretreated using a macromolecular silane coupling agent to effectively improve thermal stability, water resistance and weather resistance, while improving the surface properties of the filler and its compatibility with the matrix material. Then, the short-chain silane coupling agent of aminosilane, sulfur-containing silane, epoxysilane or methacryloxysilane further modifies the filler, enhances interfacial bonding, helps to evenly distribute, prevents powder agglomeration, optimizes dispersibility, and ultimately improves the thermal conductivity and mechanical properties of the composite material. By rationally selecting and coordinating coupling agents, the filler-matrix interface structure is optimized, and the performance of the composite material is significantly improved.

Claims

1. A secondary surface modification method for an inorganic thermally conductive powder, characterized in that: The modification method is as follows: 100 parts of inorganic thermal conductive powder are placed in a high-speed disperser with a stirring paddle, 0.1-0.9 parts of a self-developed ester-terminated macromolecular silane coupling agent are added, and the mixture is mixed at a speed of 500-1200 rpm for 1-10 minutes for preliminary modification; 0.2-1.0 parts of a short-chain silane coupling agent are then added and mixed for 1-10 minutes for secondary modification. The final powder obtained is the secondary modified inorganic thermal conductive powder. The carbon chain length of the short-chain silane coupling agent is less than 8; the self-developed ester-terminated macromolecular silane coupling agent has a structure of general formula (1), with a Si-O chain as the main chain, one end being terminated by an ester group, and the other end being terminated by an alkoxy group; In the general formula (1), R is one of an alkyl group and an aryl group; R1 is -CH3, -CH2CH3, -(CHCH3)2, -COCH3; R2 and R3 are one of -OCH3, -OCH2CH3, -O(CHCH3)2, -OCOCH3, -CH3, -CH2CH3, -(CHCH3)2; and n is a natural number of 10-100.

2. The secondary surface modification method of an inorganic thermally conductive powder according to claim 1, characterized in that: The method for preparing the self-developed ester-terminated macromolecular silane coupling agent comprises the following steps: a. Mixing terminal hydrogenated silicone oil with a solvent under nitrogen to obtain a mixed solution; adding a catalyst to the mixed solution and heating it; adding vinyl alkoxysilane at 70-80°C with a dropwise addition rate of 1 d / s; reacting at 80-90°C for 2-16 hours after the addition is complete; after the reaction is complete, distilling the crude product under reduced pressure at 0.01-0.1 MPa to remove low-boiling fractions to obtain an intermediate product; b. At room temperature, the obtained intermediate product is mixed with a solvent, a catalyst is added, and nitrogen is introduced for protection. The system is heated to 70-80°C, and acrylate is added at this temperature with a dropwise addition rate of 1 d / s. After the dropwise addition is completed, the mixture is reacted at 80-90°C for 2-16 hours. After the reaction is completed, the crude product is subjected to reduced pressure distillation at 0.01-0.1 MPa to remove low-boiling fractions to obtain an ester-terminated macromolecular silane coupling agent. The chemical reaction formulas in steps a and b are as follows: a. Reaction formula for intermediate generation b. Reaction formula for the formation of the final product 3. The secondary surface modification method of an inorganic thermally conductive powder according to claim 1, characterized in that: The inorganic thermal conductive powder is one or more of aluminum oxide, magnesium oxide, zinc oxide, silicon dioxide, titanium dioxide, aluminum hydroxide, boron nitride, and aluminum nitride.

4. The secondary surface modification method of an inorganic thermally conductive powder according to claim 1, characterized in that: The short-chain silane coupling agent has a carbon chain length of less than 8 and is specifically one of aminosilane, sulfur-containing silane, epoxysilane or methacryloxysilane.

5. The secondary surface modification method of an inorganic thermally conductive powder according to claim 1, characterized in that: The added amount of the self-developed ester-terminated macromolecular silane coupling agent is less than that of the short-chain silane coupling agent, and the total added amount does not exceed 2% of the powder mass.

6. The self-developed ester-terminated macromolecular silane coupling agent according to claim 2, characterized in that: The viscosity of the hydrogen-terminated silicone oil in step a is 20 to 10,000 mPa﹒s, and has the structure shown in general formula (2): Wherein, n in the general formula (2) is a natural number from 10 to 100.

7. The self-developed ester-terminated macromolecular silane coupling agent according to claim 2, characterized in that: The vinyl alkoxysilane in step a is one of vinyl monoalkoxysilane, vinyl dialkoxysilane or vinyl trialkoxysilane, and has a structure shown in general formula (3): In the general formula (3), R1 is one of -CH3, -CH2CH3, -(CHCH3)2, and -COCH3; R2 and R3 are one of -OCH3, -OCH2CH3, -O(CHCH3)2, -OCOCH3, -CH3, -CH2CH3, and -(CHCH3)2.

8. The ester-terminated self-developed macromolecular silane coupling agent according to claim 2, characterized in that: The acrylate in step b has a structure shown in general formula (4): In the general formula (4), R is an alkyl group or an aryl group.

9. The self-developed ester-terminated macromolecular silane coupling agent according to claim 2, characterized in that: The solvents in steps a and b are one or more of toluene, dichloromethane, chloroform or n-hexane; and the catalysts are one of Karstedt catalyst and Wilkinson catalyst.

10. The self-developed ester-terminated macromolecular silane coupling agent according to claim 2, characterized in that: The amount of the catalyst added in step a is 0.1%-5% of the terminal hydrogen silicone oil; the molar ratio of the terminal hydrogen silicone oil to vinyl alkoxysilane is 1:0.2-0.5; and the amount of the solvent added is 0.5-1.5 ml of solvent per 1 g of terminal hydrogen silicone oil.

11. The self-developed ester-terminated macromolecular silane coupling agent according to claim 2, characterized in that: In step b, the amount of the catalyst added is 0.1%-5% of the intermediate product; the molar ratio of the intermediate product to the acrylate is 0.5-2:1; and the amount of the solvent added is 0.5-1.5 ml of solvent per 1 g of the intermediate product.

12. The secondary surface modification method of an inorganic thermally conductive powder according to any one of claims 1 to 11, characterized in that: The inorganic thermally conductive powder that has undergone secondary surface modification is used to prepare thermal interface thermally conductive materials, including thermally conductive gaskets, thermally conductive gels, thermally conductive potting glue, thermally conductive silicone grease, and thermally conductive mud.

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