A heat-conducting filler, a silicone heat-conducting pouring sealant, and a preparation method and application thereof

Abstract

The application discloses a kind of heat-conducting fillers, silicone heat-conducting pouring sealant and its preparation method and application, belong to the technical field of silicone heat-conducting pouring sealant, the heat-conducting filler with secondary aluminum ash as raw material, by calcium salt realizes the soluble fluorine ion in secondary aluminum ash after fluorine removal, then hydrolysis coupling agent is carried out to its surface treatment under certain pH value, and the pouring sealant heat-conducting filler with good dispersibility and reinforcing performance is obtained.The filler retains high thermal conductivity aluminum nitride and aluminum oxide composition at the same time, and the fluorine ion leaching concentration meets the requirements, and the heat-conducting pouring sealant can be prepared after being mixed with the pouring sealant material.The application has the characteristics of simple process, low cost and easy industrialization, and opens up a new way for the resource utilization of secondary aluminum ash, a kind of hazardous waste.

Description

Technical Field

[0001] This invention belongs to the technical field of silicone thermally conductive potting compounds, specifically relating to a thermally conductive filler, a silicone thermally conductive potting compound, its preparation method, and its application. Background Technology

[0002] Secondary aluminum ash refers to aluminum-containing waste generated during aluminum smelting or processing, which still contains a certain amount of aluminum after initial treatment. This type of waste usually originates from aluminum smelting, casting, or recycling processes and contains metallic aluminum, oxides, salts, and other impurities. Because secondary aluminum ash contains a certain proportion of aluminum nitride (which slowly decomposes into ammonia gas) and soluble fluoride salts when it comes into contact with water, large-scale stockpiling can cause significant harm to soil, water bodies, and the surrounding environment. Therefore, it is included in the "National Hazardous Waste List" (2021 edition and subsequent revisions) and defined as hazardous waste, with waste category HW48 and waste codes 321-024-48 or 321-026-48.

[0003] How to turn secondary aluminum ash into a valuable resource has always been a key research focus in the industry. Chinese patent CN117623349 B discloses a method for recycling secondary aluminum ash. This method involves washing the secondary aluminum ash with water, mixing it with ammonium sulfate, calcining it, and then immersing and crystallizing it in water to obtain ammonium aluminum sulfate crystals. These crystals are then calcined at high temperature to obtain alumina. Furthermore, carboxymethyl cellulose is used to introduce active groups onto the alumina surface, improving the dispersibility and compatibility of the modified alumina in composite materials. Chinese patent CN 113652106 A discloses a wear-resistant coating made from aluminum ash and its preparation method. This method involves directly mixing water, secondary aluminum ash, kaolin, borax, and other materials, coating the mixture onto the workpiece surface, and sintering it. This yields a coating with high hardness, good wear resistance, and excellent resistance to temperature changes, achieving the goal of preparing a high-performance wear-resistant coating based on a large proportion of secondary aluminum ash. Patent CN 120328906 A discloses a concrete expansive agent based on secondary aluminum ash and its preparation method. The secondary aluminum ash is compounded with components such as attapulgite clay. The resulting expansive agent significantly reduces the expansion rate of concrete and improves its impermeability, crack resistance, and 7-day / 28-day compressive strength. The aforementioned reuse methods of secondary aluminum ash are mainly concentrated in the fields of rubber, coatings, and concrete.

[0004] Silicone thermally conductive potting compound is a two-component or one-component polymer material based on silicone. After curing, it forms a low-modulus elastomer that can deeply encapsulate and protect electronic components from moisture, vibration, and chemical corrosion. It is widely used in automotive electronics, LEDs, power modules, and solar cells. Its high thermal conductivity mainly comes from high thermal conductivity fillers. However, when the concentration of charged particles in the potting compound is high, these particles can generate induced magnetic fields in complex electromagnetic environments, causing electromagnetic interference to the protected electronic components and affecting their operation.

[0005] Given the current limited application areas and low value conversion rate of secondary aluminum ash, a new approach is to fully utilize its resources and transform it into high-value-added products. This is achieved by leveraging the high thermal conductivity of alumina and aluminum nitride in secondary aluminum ash and applying it as a thermally conductive filler in silicone thermally conductive potting compounds. However, a key challenge in using secondary aluminum ash as a thermally conductive filler in silicone thermally conductive potting compounds is reducing the concentration of free fluoride ions to ensure it does not affect the operation of electronic components and improving its compatibility with other potting compound raw materials. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a thermally conductive filler, an organosilicon thermally conductive potting compound, and its preparation method and application to solve the problems mentioned in the background art or achieve better technical effects.

[0007] In order to solve the above-mentioned technical problems, the inventors derived the technical solution of the present invention through practice and summarization. The present invention discloses a thermally conductive filler, which is an inorganic modified filler, and the raw material includes secondary aluminum ash.

[0008] Furthermore, in the secondary aluminum ash, the proportion of metallic aluminum is less than 5%, the proportion of alumina is 15-40%, and the proportion of aluminum nitride is 10-30%.

[0009] Furthermore, the particle size of the secondary aluminum ash is less than 100 mesh.

[0010] Furthermore, in any of the above-mentioned methods for preparing thermally conductive fillers, secondary aluminum ash is used as raw material. Soluble fluoride ions in the secondary aluminum ash are removed by calcium salt to obtain a mixture. The mixture is then surface-modified using a modifier to form a film on the surface of the mixture, thereby changing the surface activity of the mixture and finally obtaining the thermally conductive filler.

[0011] Furthermore, the preparation method of the thermally conductive filler includes the following steps:

[0012] S1: Mix 100 parts of secondary aluminum ash and 4-6 parts of calcium oxide, add 700-900 parts of water, keep warm and stir at 60℃ for 1-2 hours, then wash and filter, dry to obtain the mixture.

[0013] S2: Disperse 1-2 parts of KH570 into a mixed solution of ethanol and water, control the pH value to 3-5, and stir at 60℃ for 1 hour to obtain the modified solution;

[0014] S3: Mix the modified solution obtained in S2 with excess ethanol to obtain a mixture; add the mixture obtained in S1 to the mixture, stir and react at 60°C, filter and dry to obtain the thermally conductive filler.

[0015] Furthermore, in S2, the mass ratio of KH570:ethanol:water is 2:1:7.

[0016] Furthermore, an organosilicon thermally conductive potting compound, using the above-mentioned thermally conductive filler as a component, has the following dosage by weight:

[0017] 15 parts vinyl silicone oil, 10 parts dimethyl silicone oil, 1 part hydrogen-containing silicone oil, 30 parts thermally conductive filler, and 0.1 parts anti-poisoning catalyst.

[0018] Furthermore, the anti-poisoning catalyst is a Karstedt catalyst.

[0019] Furthermore, the preparation method of the organosilicon thermally conductive potting compound includes the following steps:

[0020] S1: At room temperature, first add 15 parts of vinyl silicone oil, 10 parts of dimethyl silicone oil and 1 part of hydrogen-containing silicone oil to a beaker and mix thoroughly for 10 minutes at a speed of 1200 r / min.

[0021] S2: Add 30 parts of thermally conductive filler and 0.1 parts of anti-poisoning catalyst to a beaker and mix thoroughly at 1200 r / min for 10 min to obtain silicone thermally conductive potting compound.

[0022] Furthermore, the aforementioned silicone thermally conductive potting compound is used in electronic components.

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

[0024] (1) This invention addresses the problems of the narrow scope of utilization and low value conversion rate of secondary aluminum ash, which is a solid waste. By utilizing the high thermal conductivity of aluminum oxide and the high content of aluminum nitride in secondary aluminum ash, the invention applies secondary aluminum ash as a thermally conductive filler for organosilicon thermally conductive potting compound in the potting compound field. This is a new way to make it fully resource-based and transform it into high added value.

[0025] (2) The present invention uses secondary aluminum ash as raw material, first undergoes solid fluorine treatment, and then performs surface modification to finally prepare an organosilicon thermally conductive potting compound with good thermal conductivity and mechanical properties and significantly reduced free fluoride ion concentration. When applied to electronic components and other fields, it can avoid electromagnetic interference to the protected electronic components and affect their operation.

[0026] (3) This invention utilizes surface modification technology. After coating the aluminum ash surface with a silane coupling agent to form a film, the activity of the aluminum ash surface is changed, making the aluminum ash surface compatible with organic matter, thereby improving the bonding force between the two, that is, enhancing the interfacial force. In the system of this invention, the interfacial force affects the thermal resistance of heat transfer. The stronger the bonding force, the smaller the thermal resistance, and the better the thermal conductivity of the entire system.

[0027] (4) In this invention, aluminum ash with high thermal conductivity is incorporated into organosilicon with low thermal conductivity. After mixing, a higher proportion of aluminum ash will be continuously distributed in the organosilicon to form thermal bridges, which guide heat transfer through the aluminum ash, and the overall thermal conductivity will be significantly improved. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the preparation process of the silicone thermally conductive potting compound of the present invention.

[0029] Figure 2 This is a physical image of the organosilicon thermally conductive potting compound prepared from the thermally conductive filler obtained in Example 1 of the present invention.

[0030] Among them, (a) is the silicone thermally conductive potting compound before stretching; (b) is the silicone thermally conductive potting compound that broke after stretching; and (c) is a rectangular silicone thermally conductive potting compound block.

[0031] Figure 3 The properties (thermal conductivity, tensile strength, and F) of the organosilicon thermally conductive potting compound prepared from the thermally conductive fillers obtained in Examples 1-6 of this invention are as follows: - Leaching concentration test chart. Detailed Implementation

[0032] To make the above-mentioned objectives, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to specific examples.

[0033] Unless otherwise specified, all raw materials or reagents used in the following examples are commercially available products or products prepared using conventional methods.

[0034] In secondary aluminum ash, the proportion of metallic aluminum is less than 5%, the proportion of alumina is 15-40%, and the proportion of aluminum nitride is 10-30%; the particle size of secondary aluminum ash is less than 100 mesh.

[0035] The anti-poisoning catalyst is a Karstedt catalyst.

[0036] The test methods for the following silicone thermally conductive potting compounds are as follows:

[0037] Thermal conductivity (W / (m·k)) test: Tested according to GB / T10297-2015;

[0038] Shore A hardness test: Tested according to GB / T531-200;

[0039] Tensile strength (MPa) test: dumbbell-shaped specimens were used, and the test was conducted according to GB / T528-2008;

[0040] Elongation at break (%) test: dumbbell-shaped specimens were used, and the test was conducted according to GB / T528-2008;

[0041] Determination of fluoride in leachate of potting compound scraps: Test according to GB / T15555.5-1995.

[0042] Example 1

[0043] A method for preparing an organosilicon thermally conductive potting compound and thermally conductive filler, such as... Figure 1 As shown, the steps are as follows:

[0044] (1) Mix 100 parts of secondary aluminum ash and 4 parts of calcium oxide, add 700 parts of water, keep warm and stir at 60°C for 1 hour, wash and filter, put into an oven to dry, and obtain the mixture.

[0045] (2) Disperse 1 part of KH570 into a mixed solution of ethanol and water (the mass ratio of KH570:ethanol:water is 2:1:7), control the pH value to 3 by pH adjuster, keep warm at 60℃ and stir for 1h to obtain the modified solution;

[0046] (3) Mix the modified solution obtained in step (2) with excess ethanol to obtain a mixture; then add 100 parts of the mixture obtained in step (1) to the mixture, stir for 2 hours under the condition of keeping warm at 60°C, filter and dry to obtain the organosilicon thermally conductive potting compound thermally conductive filler.

[0047] Example 2

[0048] A method for preparing an organosilicon thermally conductive potting compound and thermally conductive filler, comprising the following steps:

[0049] (1) Mix 100 parts of secondary aluminum ash and 6 parts of calcium oxide, add 900 parts of water, keep warm and stir at 60°C for 2 hours, wash and filter, put into an oven to dry, and obtain the mixture.

[0050] (2) Disperse 1 part of KH570 into a mixed solution of ethanol and water (the mass ratio of KH570:ethanol:water is 2:1:7), control the pH value to 3 by pH adjuster, keep warm at 60℃ and stir for 1h to obtain the modified solution;

[0051] (3) Mix the modified solution obtained in step (2) with excess ethanol to obtain a mixture; then add 100 parts of the mixture obtained in step (1) to the mixture, stir for 2 hours under the condition of keeping warm at 60°C, filter and dry to obtain the organosilicon thermally conductive potting compound thermally conductive filler.

[0052] Example 3

[0053] A method for preparing an organosilicon thermally conductive potting compound and thermally conductive filler, comprising the following steps:

[0054] (1) Mix 100 parts of secondary aluminum ash and 4 parts of calcium oxide, add 700 parts of water, keep warm and stir at 60°C for 1 hour, wash and filter, put into an oven to dry, and obtain the mixture.

[0055] (2) Disperse 2 parts of KH570 into a mixed solution of ethanol and water (the mass ratio of KH570:ethanol:water is 2:1:7), control the pH value to 3 by pH adjuster, keep warm at 60℃ and stir for 1h to obtain the modified solution;

[0056] (3) Mix the modified solution obtained in step (2) with excess ethanol to obtain a mixture; then add 100 parts of the mixture obtained in step (1) to the mixture, stir for 2 hours under the condition of keeping warm at 60°C, filter and dry to obtain the organosilicon thermally conductive potting compound thermally conductive filler.

[0057] Example 4

[0058] A method for preparing an organosilicon thermally conductive potting compound and thermally conductive filler, comprising the following steps:

[0059] (1) Mix 100 parts of secondary aluminum ash and 4 parts of calcium oxide, add 900 parts of water, keep warm and stir at 60°C for 1 hour, wash and filter, put into an oven to dry, and obtain the mixture.

[0060] (2) Disperse 2 parts of KH570 into a mixed solution of ethanol and water (the mass ratio of KH570:ethanol:water is 2:1:7), control the pH value to 4 with a pH adjuster, keep warm at 60℃ and stir for 1h to obtain a modified solution;

[0061] (3) Mix the modified solution obtained in step (2) with excess ethanol to obtain a mixture; then add 100 parts of the mixture obtained in step (1) to the mixture, stir for 2 hours under the condition of keeping warm at 60°C, filter and dry to obtain the organosilicon thermally conductive potting compound thermally conductive filler.

[0062] Example 5

[0063] A method for preparing an organosilicon thermally conductive potting compound and thermally conductive filler, comprising the following steps:

[0064] (1) Mix 100 parts of secondary aluminum ash and 6 parts of calcium oxide, add 700 parts of water, keep warm and stir at 60°C for 2 hours, wash and filter, put into an oven to dry, and obtain the mixture.

[0065] (2) Disperse 1 part of KH570 into a mixed solution of ethanol and water (the mass ratio of KH570:ethanol:water is 2:1:7), control the pH value to 5 by pH adjuster, keep warm at 60℃ and stir for 1h to obtain the modified solution;

[0066] (3) Mix the modified solution obtained in step (2) with excess ethanol to obtain a mixture; then add 100 parts of the mixture obtained in step (1) to the mixture, stir for 2 hours under the condition of keeping warm at 60°C, filter and dry to obtain the organosilicon thermally conductive potting compound thermally conductive filler.

[0067] Example 6

[0068] A method for preparing an organosilicon thermally conductive potting compound and thermally conductive filler, comprising the following steps:

[0069] (1) Mix 100 parts of secondary aluminum ash and 6 parts of calcium oxide, add 700 parts of water, keep warm and stir at 60°C for 1 hour, wash and filter, put into an oven to dry, and obtain the mixture.

[0070] (2) Disperse 1 part of KH570 into a mixed solution of ethanol and water (the mass ratio of KH570:ethanol:water is 2:1:7), control the pH value to 3 by pH adjuster, keep warm at 60℃ and stir for 1h to obtain the modified solution;

[0071] (3) Mix the modified solution obtained in step (2) with excess ethanol to obtain a mixture; then add 100 parts of the mixture obtained in step (1) to the mixture, stir for 2 hours under the condition of keeping warm at 60°C, filter and dry to obtain the organosilicon thermally conductive potting compound thermally conductive filler.

[0072] The thermally conductive fillers obtained in the above six embodiments were applied to the preparation of silicone thermally conductive potting compounds. Specifically, the silicone thermally conductive potting compound prepared in Example 1 was as follows: Figure 2 As shown.

[0073] The components and weight parts of each raw material of the organosilicon thermally conductive potting compound are as follows: 15 parts vinyl silicone oil, 10 parts dimethyl silicone oil, 1 part hydrogen-containing silicone oil, 30 parts thermally conductive filler, and 0.1 parts anti-poisoning catalyst.

[0074] The preparation method of the organosilicon thermally conductive potting compound is as follows: At room temperature, first add 15 parts of vinyl silicone oil, 10 parts of dimethyl silicone oil and 1 part of hydrogen-containing silicone oil to a beaker, and mix thoroughly for 10 minutes at 1200 rpm in a magnetic stirrer. Then add 30 parts of thermally conductive filler and 0.1 parts of anti-poisoning catalyst to the beaker, and mix thoroughly for 10 minutes at 1200 rpm to obtain the organosilicon thermally conductive potting compound. Pour the organosilicon thermally conductive potting compound into a mold, then remove bubbles using a vacuum machine, and keep it at room temperature for 20 minutes to obtain the organosilicon thermally conductive potting compound block.

[0075] Comparative Example 1

[0076] Comparative Example 1 was prepared using silicone potting compound raw materials that do not contain thermally conductive fillers.

[0077] The components and weight parts of each raw material in the silicone potting compound are as follows:

[0078] 15 parts vinyl silicone oil, 10 parts dimethyl silicone oil, 1 part hydrogen-containing silicone oil, and 0.1 parts anti-poisoning catalyst.

[0079] The preparation method of the silicone potting compound is as follows: At room temperature, 15 parts of vinyl silicone oil, 10 parts of dimethyl silicone oil and 1 part of hydrogen-containing silicone oil are added to a beaker and mixed thoroughly for 10 minutes at 1200 rpm in a magnetic stirrer. Then, 0.1 parts of anti-poisoning catalyst are added to the beaker and mixed thoroughly for 10 minutes at 1200 rpm to obtain the silicone thermally conductive potting compound. The silicone thermally conductive potting compound is poured into a mold, and then the bubbles are removed by a vacuum machine. After being kept at room temperature for 20 minutes, the silicone potting compound block is obtained.

[0080] Comparative Example 2

[0081] Secondary aluminum ash that has only undergone modification is used as the thermally conductive filler in the silicone thermally conductive potting compound.

[0082] The preparation method of the thermally conductive filler in this silicone thermally conductive potting compound is as follows:

[0083] (1) Disperse 1 part of KH570 into a mixed solution of ethanol and water (the mass ratio of KH570:ethanol:water is 2:1:7), control the pH value to 4 by pH adjuster, keep warm at 60℃ and stir for 1h to obtain the modified solution;

[0084] (2) The modified solution obtained in step (2) is mixed with excess ethanol to obtain a mixture; then 100 parts of secondary aluminum ash are added to the mixture, and after stirring at 60°C for 2 hours, it is filtered and dried to obtain the thermally conductive filler.

[0085] Comparative Example 3

[0086] Secondary aluminum ash that has only undergone solid fluorine treatment is used as the thermally conductive filler in the silicone thermally conductive potting compound.

[0087] The preparation method of the thermally conductive filler in this silicone thermally conductive potting compound is as follows:

[0088] Mix 100 parts of secondary aluminum ash with 4 parts of calcium oxide, add 900 parts of water, keep warm at 60℃ and stir for 2 hours, then wash and filter, and dry in an oven to obtain thermally conductive filler.

[0089] The thermally conductive fillers obtained from Comparative Examples 2 and 3 were used in the preparation of silicone thermally conductive potting compounds.

[0090] The components and weight proportions of each raw material in the silicone thermally conductive potting compound are as follows:

[0091] 15 parts vinyl silicone oil, 10 parts dimethyl silicone oil, 1 part hydrogen-containing silicone oil, 30 parts thermally conductive filler and 0.1 parts anti-poisoning catalyst.

[0092] The preparation method of this silicone thermally conductive potting compound is as follows:

[0093] At room temperature, 15 parts of vinyl silicone oil, 10 parts of dimethyl silicone oil and 1 part of hydrogen-containing silicone oil are added to a beaker and mixed thoroughly for 10 minutes at 1200 rpm in a magnetic stirrer. Then, 30 parts of thermally conductive filler and 0.1 parts of anti-poisoning catalyst are added to the beaker and mixed thoroughly for 10 minutes at 1200 rpm to obtain an organosilicon thermally conductive potting compound. The organosilicon thermally conductive potting compound is poured into a mold, and then degassed using a vacuum machine. After being kept at room temperature for 20 minutes, an organosilicon thermally conductive potting compound block is obtained.

[0094] The organosilicon thermally conductive potting compounds prepared in Examples 1-6 and Comparative Examples 1-3 were tested for thermal conductivity (W / (m·K)), Shore A hardness, tensile strength (MPa), elongation at break (%), and F. - The leaching concentration (mg / L) test results are shown in Table 1 below. Figure 3 As shown.

[0095] Table 1 Examples 1-6 and Comparative Examples 1-3

[0096] Test results of various properties of the prepared silicone thermally conductive potting compound block

[0097] The test results are shown in Table 1 and Figure 3 As shown, the comparison between the examples and Comparative Example 1 demonstrates that the thermally conductive filler prepared in this invention, as a modifying material, can effectively improve the thermal conductivity, hardness, and tensile strength of the potting compound block.

[0098] Secondary aluminum ash (mainly a mixture of alumina, aluminum nitride, etc.) is a highly thermally conductive inorganic material, while organosilicon, as an organic material, has low thermal conductivity due to weak intermolecular bonding. The significant differences in their physicochemical properties lead to a lack of affinity and compatibility, resulting in a weak bonding force between them (primarily intermolecular forces). This invention utilizes surface modification technology, employing a silane coupling agent to coat the aluminum ash surface, altering its activity and enabling compatibility with the organic material, thereby enhancing the bonding force and interfacial interaction. In this system, interfacial interaction affects the thermal resistance of heat transfer; stronger bonding results in lower thermal resistance and improved overall thermal conductivity. Simultaneously, the high thermal conductivity of the aluminum ash, when incorporated into the low thermal conductivity of the organosilicon, creates thermal bridges through which heat is transferred, significantly improving the overall thermal conductivity.

[0099] A suitable and uniformly dispersed rigid filler can effectively bear and transfer stress, hinder the propagation of microcracks, and play a certain reinforcing role in the matrix. The filler itself has a much higher modulus than the resin matrix, and its increased proportion directly and effectively improves the overall modulus of the composite material, which also affects mechanical properties. The stronger and more robust the bonding force, the better the mechanical properties will be. Compared with organosilicon, aluminum ash has much higher hardness and mechanical properties. After mixing and curing to form a whole, the overall performance is a combination of both, and therefore better than a simple organosilicon block. However, the bonding force between organosilicon and aluminum ash is weak because their physical properties are incompatible, and they will break first at the interface under mechanical load. After modifying aluminum ash with a silane coupling agent, the bonding force between the modified aluminum ash and organosilicon will be significantly enhanced.

[0100] The comparison between the examples and Comparative Example 2 shows that, in the preparation of the thermally conductive filler of the present invention, the fluoride ion curing and removal process for secondary aluminum ash can significantly reduce the fluoride content of the potting compound. - Leaching concentration.

[0101] The comparison between the examples and Comparative Example 3 shows that the modified thermally conductive filler of the present invention can improve the mechanical properties of the potting compound block.

[0102] The fluorine fixation mechanism of this invention mainly involves calcium oxide and dissolved F. - The reaction produces water-insoluble calcium fluoride, thus achieving fluoride fixation. The fluoride fixation mechanism mainly utilizes the precipitation reaction between calcium ions and fluoride ions to eliminate the leaching toxicity of fluorides in secondary aluminum ash, i.e., Ca... 2+ +2F - =CaF2↓, the reaction produces hydroxide precipitate against F - Adsorption, ion exchange, and flocculation can also reduce F - concentration.

[0103] Excess calcium oxide will hydrolyze to form calcium hydroxide, which has poorer mechanical properties and lower thermal conductivity than aluminum nitride. This calcium hydroxide is an amorphous precipitate that can adsorb a certain amount of F. - While achieving solid fluorine, excessive amorphous calcium hydroxide can cause a decrease in the thermal conductivity and mechanical properties of the gel block, including its hardness. Therefore, a comparison between Examples 1 and 6 reveals that a decrease in leaching concentration also leads to a decrease in mechanical properties.

[0104] The comparisons between Examples 2 and 5, and between Examples 1 and 4, show that when the water volume varies from 700 to 900, the leaching concentration fluctuates within a certain range. This is because, on the one hand, increasing the solvent volume facilitates faster solute dissolution, provides more sufficient dispersion space, and increases the reaction contact area, thus promoting the dissolution of F. - The faster the calcium oxide escapes from the aluminum ash to participate in the fluorine fixation reaction, the better the fluorine fixation process proceeds, thus reducing the leaching concentration. On the other hand, in systems with less water, due to excess calcium oxide, the Ca produced by the system... 2+ High concentrations can further reduce F through the common ion effect. - Concentration, and within a limited reaction time, excess CaO can accelerate the reaction rate. These two trends are exactly opposite, leading to the conclusion, based on experiments, that under conditions of 4-6 parts calcium oxide and 700-900 parts water treatment, after solid fluoride treatment, the F content of the potting compound block using it as filler... - The leaching concentration test value fluctuated around 1 mg / L, with slight differences in the fluctuation.

Claims

1. A thermally conductive filler, characterized in that, The thermally conductive filler is an inorganic modified filler, and the raw material includes secondary aluminum ash.

2. The thermally conductive filler according to claim 1, characterized in that, In the secondary aluminum ash, the proportion of metallic aluminum is less than 5%, the proportion of alumina is 15-40%, and the proportion of aluminum nitride is 10-30%.

3. The thermally conductive filler according to claim 1, characterized in that, The particle size of the secondary aluminum ash is less than 100 mesh.

4. The method for preparing the thermally conductive filler according to any one of claims 1 to 3, characterized in that, Using secondary aluminum ash as raw material, soluble fluoride ions in the secondary aluminum ash are removed by calcium salt to obtain a mixture. The mixture is then surface-modified by a modifier, and a film is formed on the surface of the mixture to change the surface activity, ultimately yielding a thermally conductive filler.

5. The method for preparing the thermally conductive filler according to claim 4, characterized in that, The steps are as follows: S1: Mix 100 parts of secondary aluminum ash and 4-6 parts of calcium oxide, add 700-900 parts of water, keep warm and stir at 60℃ for 1-2 hours, then wash and filter, dry to obtain the mixture. S2: Disperse 1-2 parts of KH570 into a mixed solution of ethanol and water, control the pH value to 3-5, and stir at 60℃ for 1 hour to obtain the modified solution; S3: Mix the modified solution obtained in S2 with excess ethanol to obtain a mixture; add the mixture obtained in S1 to the mixture, stir and react at 60°C, filter and dry to obtain the thermally conductive filler.

6. The method for preparing the thermally conductive filler according to claim 5, characterized in that, In S2, the mass ratio of KH570:ethanol:water is 2:1:

7.

7. A silicone thermally conductive potting compound, comprising the thermally conductive filler according to any one of claims 1 to 3, characterized in that, The amounts of each component, by weight, are as follows: 15 parts vinyl silicone oil, 10 parts dimethyl silicone oil, 1 part hydrogen-containing silicone oil, 30 parts thermally conductive filler, and 0.1 parts anti-poisoning catalyst.

8. The silicone thermally conductive potting compound according to claim 7, characterized in that, The anti-poisoning catalyst is a Karstedt catalyst.

9. The method for preparing the organosilicon thermally conductive potting compound according to claim 7 or 8, characterized in that, The steps are as follows: S1: At room temperature, first add 15 parts of vinyl silicone oil, 10 parts of dimethyl silicone oil and 1 part of hydrogen-containing silicone oil to a beaker and mix thoroughly for 10 minutes at a speed of 1200 r / min. S2: Add 30 parts of thermally conductive filler and 0.1 parts of anti-poisoning catalyst to a beaker and mix thoroughly at 1200 r / min for 10 min to obtain silicone thermally conductive potting compound.

10. The application of the silicone thermally conductive potting compound according to claim 7 or 8 in electronic components.

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