Lightweight anti-settling type silicone heat-conducting pouring sealant powder filler and preparation method thereof

Abstract

The application discloses a light-weight anti-settling type silicone heat-conducting pouring sealant powder filler and a preparation method thereof, and belongs to the technical field of heat-conducting pouring sealant materials. The powder filler is prepared by mixing 70-80 microns of aluminum hydroxide, 50-70 microns of silicon dioxide, 7-10 microns of aluminum hydroxide and 2-3 microns of aluminum oxide, and then adding a surface modifier for dry modification. The application effectively reduces the packing density of the filler, inhibits the settlement and stratification, and maintains good fluidity and heat-conducting performance by means of four-stage particle size grading and the combination of aluminum hydroxide / silicon dioxide / aluminum oxide three-material compounding and dry surface modification. After the obtained powder filler is compounded with vinyl silicone oil, the density of the pouring sealant can be as low as 2.02 g / cm3, the 72-hour settlement amount is only 0.3 mm, the heat-conducting coefficient reaches 1.46 W / m.K, and the pouring sealant has the advantages of light weight, anti-settling, high heat-conducting, low viscosity, halogen-free and flame-retardant. The powder filler has simple preparation process, low cost and wide application.

Description

Technical Field

[0001] This invention relates to the field of potting compound powder filler technology, and in particular to a lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler and its preparation method. Background Technology

[0002] Anti-settling performance is one of the core requirements for potting compounds (especially high thermal conductivity, high filler silicone potting compounds), directly affecting product stability, processability, and final performance. Meanwhile, with the development of lightweight and energy-saving technologies in new energy vehicles, energy storage, and electronic devices, traditional high-filler thermally conductive potting compounds, due to their high filler density and specific gravity, result in heavy overall products, hindering equipment lightweighting, increasing load and energy consumption, and becoming a prominent pain point in the industry. Thermally conductive silicone potting compounds are mainly composed of fillers, organic carriers, and modifiers. To meet potting requirements, the system needs to maintain suitable fluidity. Numerous studies have shown that potting compounds with low viscosity and uneven dispersion are highly prone to filler sedimentation during long-term storage. Commonly used fillers such as alumina and silica powder have significantly higher densities than silicone matrices (such as vinyl silicone oil). During storage or standing, they gradually settle, leading to the precipitation of upper silicone oil and the caking of lower fillers, resulting in severely uneven filler distribution. This, in turn, causes the thermal conductivity network to break, localized thermal efficiency to decrease, and may trigger overheating failure of electronic components. Meanwhile, excessive accumulation of the lower layer of filler after settling can lead to excessively high local viscosity, resulting in poor fluidity during potting, making it difficult to fill tiny gaps and complex structures, and affecting sealing and heat dissipation.

[0003] Thermally conductive potting compound powder is the core component of thermally conductive potting compound. It serves as a dispersion carrier for thermally conductive fillers, ensuring uniform distribution of fillers and forming effective thermal conduction pathways. After base material refining, the fillers and silicone oil are processed to form the base material. Organosilicon is weather-resistant and moisture-proof, effectively solving the storage and transportation problems of fillers.

[0004] Traditional thermally conductive potting compounds suffer from insufficient anti-settling properties, high density, high specific gravity, and low weight reduction, resulting in the following prominent problems in actual production and application:

[0005] 1. Performance defects after curing: Filler sedimentation leads to colloid density stratification, uneven mechanical properties, large differences in local elastic modulus, and easy stress concentration or even cracking.

[0006] 2. Poor sealing effect: Settlement causes local viscosity to be too high and fluidity to be insufficient, which cannot fully fill the tiny gaps and the gaps between dense components, reducing the reliability of sealing and heat dissipation;

[0007] 3. Poor product consistency: Uneven distribution of fillers leads to poor batch stability, making it difficult to meet the requirements of large-scale production and long-term reliability;

[0008] 4. High specific gravity, which is not conducive to lightweighting: The overall weight is large, which does not conform to the development trend of lightweighting, low energy consumption, energy conservation and environmental protection in new energy, automotive electronics and energy storage equipment. Summary of the Invention

[0009] The purpose of this invention is to provide a lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler and its preparation method to solve the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] A lightweight, anti-settling, silicone thermally conductive potting compound powder filler, characterized in that: the powder filler is prepared by mixing components containing the following particle size ranges and materials and then dry-modifying them with a surface modifier:

[0012] 200-500 parts of 70-80 micron aluminum hydroxide;

[0013] 100-400 parts of 50-70 micron silica;

[0014] 100-400 parts of 7-10 micron aluminum hydroxide;

[0015] 200-500 parts of ordinary alumina (2-3 microns);

[0016] 1-20 parts of surface modifier.

[0017] As further described in this invention, the surface modifier is one of a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent.

[0018] As further described in this invention, the components of the powder filler and the surface modifier are as follows:

[0019] 300 parts of 70-80 micron aluminum hydroxide;

[0020] 200 parts of 50-70 micron silica;

[0021] 200 parts of 7-10 micron aluminum hydroxide;

[0022] 300 parts of ordinary alumina with a diameter of 2-3 micrometers;

[0023] 10 parts of surface modifier.

[0024] A method for preparing a lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler includes the following steps:

[0025] (1) Add 70-80 micrometer aluminum hydroxide, 50-70 micrometer silicon dioxide, 7-10 micrometer aluminum hydroxide and 2-3 micrometer aluminum oxide into a high-speed mixer and stir to mix evenly to obtain powder filler A;

[0026] (2) Add the surface modifier to the powder filler A and continue stirring to carry out dry modification to obtain the lightweight anti-settling organosilicon thermally conductive potting compound powder filler.

[0027] In a further description of the present invention, in step (1), the stirring speed is 20-40 Hz / min and the stirring time is 1-5 minutes; in step (2), the stirring speed is 10-50 Hz / min and the stirring time is 2-8 minutes.

[0028] An organosilicon thermally conductive potting compound comprising vinyl silicone oil and the aforementioned lightweight, anti-settling organosilicon thermally conductive potting compound powder filler.

[0029] Furthermore, the vinyl silicone oil is 100 parts of 100cp vinyl silicone oil and 450 parts of the powder filler described above.

[0030] The beneficial effects of this invention are as follows:

[0031] 1. Excellent lightweight effect, significantly reducing product weight.

[0032] This invention improves the porosity of the powder packing system and effectively reduces the packing density by constructing a large-particle-size support skeleton using 70-80 micrometer coarse-particle-size aluminum hydroxide. At the same time, it further reduces the weight of the overall packing system by partially replacing high-density aluminum oxide with lower-density aluminum hydroxide and silicon dioxide.

[0033] 2. Excellent anti-settling properties ensure product stability during storage and use.

[0034] This invention constructs a continuous and stable powder packing skeleton through a four-level particle size distribution design of "70-80μm coarse powder + 50-70μm medium-coarse powder + 7-10μm fine powder + 2-3μm micro powder". The coarse powder forms a rigid support network, the medium-coarse and fine powders fill the gaps step by step, and the micro powder fills the interfacial gaps, effectively suppressing the settling tendency of the filler during storage or settling.

[0035] 3. Good fluidity and process adaptability

[0036] This invention effectively reduces the contact points and frictional resistance between fine powders by constructing a coarse-grained skeleton, avoiding a sharp increase in viscosity due to overfilling. Simultaneously, dry surface modification treatment improves the interfacial compatibility between the powder and the silicone oil matrix, further reducing the system viscosity. 4. Maintaining high thermal conductivity, the thermally conductive network remains continuous and intact.

[0037] Although this invention uses low-density aluminum hydroxide and silicon dioxide, the continuous stacking structure built with four particle size gradations, combined with the aluminum oxide-dominated thermal conductivity pathway, effectively forms a complete thermal conductivity network. 5. It also possesses halogen-free flame-retardant properties, making it safe and environmentally friendly.

[0038] This invention uses aluminum hydroxide as one of the main fillers. When aluminum hydroxide decomposes upon heating, it releases water of crystallization, simultaneously absorbing heat and diluting flammable gases, thus achieving a halogen-free flame-retardant effect. Testing shows that the product of this invention achieves a UL94V0 flame-retardant rating, meeting the environmental requirements for flame-retardant safety in the electronics and electrical appliance industry.

[0039] 6. Excellent overall performance, surpassing existing technologies.

[0040] Comprehensive comparison shows that this invention achieves an optimal balance in four core indicators: density (2.02 g / cm³), sedimentation (0.3 mm), viscosity (4280 mPa·s), and thermal conductivity (1.46 W / m·K). In contrast, the pure alumina system has high density and severe sedimentation; the pure silica system has poor thermal conductivity and excessively high viscosity; the pure aluminum hydroxide system has insufficient thermal conductivity and relatively high viscosity; and commercially available anti-settling products have high density but still significant sedimentation. This invention, with a single technical solution, simultaneously solves the technical challenges of balancing "lightweight" and "anti-settling" and the contradiction between "low viscosity" and "high filler content" in existing technologies, achieving significant synergistic technical effects.

[0041] 7. The preparation process is simple and suitable for industrial production.

[0042] This invention employs a dry modification process, continuously completing powder mixing and surface modification in the same equipment (high-speed mixer). It requires no solvents, no heating, and no post-processing, resulting in a short process flow, simple operation, low cost, and ease of large-scale industrial production. Furthermore, the product is in powder form, weather-resistant and moisture-proof, facilitating storage and transportation. Customers only need to mix and disperse it with silicone oil, making operation convenient and quick. Detailed Implementation

[0043] The present invention will be further described below:

[0044] Example 1:

[0045] I. Powder filler formulation (parts by weight)

[0046] 70-80μm aluminum hydroxide: 250 parts;

[0047] 50-70μm silica: 200 parts;

[0048] 7-10μm aluminum hydroxide: 300 parts;

[0049] 2-3μm alumina: 250 parts;

[0050] Surface modifier (γ-glycidyl etheroxypropyltrimethoxysilane, silane coupling agent KH-560): 8 parts.

[0051] II. Oilseed Formula

[0052] 100cp vinyl silicone oil: 100 parts

[0053] III. Preparation Method

[0054] (1) Weigh 70-80μm aluminum hydroxide, 50-70μm silicon dioxide, 7-10μm aluminum hydroxide and 2-3μm aluminum oxide according to the above powder filler formula, add them to a high-speed mixer, and mix for 3 minutes at a stirring speed of 30HZ / MIN to obtain powder filler A.

[0055] (2) Add the surface modifier evenly to the powder filler A, and continue mixing for 5 minutes at a stirring speed of 25HZ / MIN to carry out dry modification and obtain lightweight anti-settling organosilicon thermally conductive potting compound powder filler.

[0056] (3) Take 315g of the above powder filler (converted to the proportion when the total weight is 450 parts) and 70g of 100cp vinyl silicone oil (corresponding to 100 parts) and place them in a disperser. Disperse at 800rpm for 5 minutes, and then degas at a vacuum of 0.08MPa for 8 minutes to ensure that all materials are mixed evenly. The resulting silicone thermally conductive potting compound sample is recorded as Example 1.

[0057] IV. Performance Testing

[0058] The potting compound sample from Example 1 was tested and found to have the following properties: density 2.02 g / cm³, thermal conductivity 1.46 W / m·K, viscosity 4280 mPa·s, and sedimentation rate of 0.3 mm after 72 hours. This sample exhibits good flowability, anti-settling properties, and low density, demonstrating excellent overall performance.

[0059] Example 2:

[0060] This embodiment is basically the same as Embodiment 1, except that the weight ratio of the powder filler is different, as detailed below:

[0061] 70-80μm aluminum hydroxide: 400 parts;

[0062] 50-70μm silica: 150 parts;

[0063] 7-10μm aluminum hydroxide: 150 parts;

[0064] 2-3μm alumina: 300 parts;

[0065] Surface modifier (titanium ester coupling agent, model NDZ-101): 12 parts.

[0066] The preparation method was the same as in Example 1. The resulting potting compound sample was designated as Example 2.

[0067] Performance testing: density 2.11 g / cm³, thermal conductivity 1.52 W / m·K, viscosity 4650 mPa·s, 72h sedimentation 0.4 mm. In this embodiment, by increasing the ratio of coarse-grained aluminum hydroxide and aluminum oxide, the thermal conductivity was slightly improved, while the density and sedimentation remained at excellent levels.

[0068] Example 3:

[0069] This embodiment is basically the same as Embodiment 1, except that the surface modifier is an aluminate coupling agent (model DL-411), and the dosage is 15 parts. The rest are the same. The resulting potting compound sample is recorded as Embodiment 3.

[0070] Performance tests: density 2.04 g / cm³, thermal conductivity 1.44 W / m·K, viscosity 4450 mPa·s, sedimentation rate 0.3 mm after 72 hours. This example demonstrates that different coupling agents can achieve good modification effects, and the product performance is stable.

[0071] Comparative Example 1 (Pure Alumina System):

[0072] A single alumina filler was used (2-3 μm ordinary alumina and 50-70 μm alumina were mixed at a mass ratio of 1:1), and the total filler amount was the same as in Example 1. Other conditions (silicone oil, preparation process) were exactly the same as in Example 1.

[0073] Performance tests: density 2.51 g / cm³, thermal conductivity 1.58 W / m·K, viscosity 4360 mPa·s, sedimentation over 72 hours 4.8 mm. The results indicate that the pure alumina system has high density and severe sedimentation, which is detrimental to lightweighting and results in poor storage stability.

[0074] Comparative Example 2 (Pure Silicon Dioxide System):

[0075] A single silica filler (50-70μm silica and 2-3μm silica mixed at a mass ratio of 1:1) was used, and the total filler amount was the same as in Example 1. Other conditions were the same as in Example 1.

[0076] Performance tests: density 1.91 g / cm³, thermal conductivity 1.35 W / m·K, viscosity 8540 mPa·s, sedimentation amount after 72 hours 3.6 mm. The results indicate that although the pure silica system has a low density, it suffers from insufficient thermal conductivity, high viscosity, and significant sedimentation.

[0077] Comparative Example 3 (Pure Aluminum Hydroxide System):

[0078] A single aluminum hydroxide filler was used (70-80μm aluminum hydroxide and 7-10μm aluminum hydroxide were mixed at a mass ratio of 1:1), and the total filler content was the same as in Example 1. Other conditions were the same as in Example 1.

[0079] Performance tests: density 1.82 g / cm³, thermal conductivity 1.38 W / m·K, viscosity 6760 mPa·s, sedimentation amount after 72 hours 0.8 mm. The results show that the pure aluminum hydroxide system has the lowest density, but insufficient thermal conductivity and excessively high viscosity. Although its anti-settling properties are better than pure aluminum oxide, they are still inferior to those of this invention.

[0080] Comparative Example 4 (Commercially available anti-settling products):

[0081] A commercially available anti-settling silicone thermally conductive potting compound powder filler (nominal thermal conductivity ≥1.4W / m·K) was selected and compounded using the same silicone oil and preparation process as in Example 1 to obtain a sample.

[0082] Performance tests: density 2.47 g / cm³, thermal conductivity 1.42 W / m·K, viscosity 5630 mPa·s, 72-hour sedimentation 1.8 mm. The results show that while commercially available products have some anti-settling effect, they are high in density and insufficiently lightweight, and their sedimentation is still significantly higher than that of this invention.

[0083] Comparative Example 5 (Changing Particle Size Combination – Lacking Coarse Particle Size Skeleton):

[0084] This comparative example is basically the same as Example 1, except that the particle size combination of the powder filler is adjusted to: 50-60μm aluminum hydroxide, 30-40μm silica, 5-6μm aluminum hydroxide, and 1-2μm alumina (all four particle sizes are below the range of this invention). The weight parts of each material are the same as in Example 1. Other conditions are the same as in Example 1.

[0085] Performance testing: density 2.28 g / cm³, thermal conductivity 1.41 W / m·K, viscosity 6120 mPa·s, 72h sedimentation 2.3 mm. The results indicate that the lack of a 70-80 μm coarse-grained skeleton leads to increased bulk density, higher viscosity, and significantly increased sedimentation, making it impossible to simultaneously achieve lightweighting and anti-settling properties.

[0086] Comparative Example 6 (Change in ratio – insufficient coarse powder):

[0087] This comparative example is basically the same as Example 1, except that the powder filler ratio is: 50 parts of 70-80μm aluminum hydroxide, 400 parts of 50-70μm silica, 400 parts of 7-10μm aluminum hydroxide, and 150 parts of 2-3μm alumina. Other conditions are the same as in Example 1.

[0088] Performance tests: density 2.35 g / cm³, thermal conductivity 1.45 W / m·K, viscosity 5480 mPa·s, 72h settling amount 1.5 mm. The results show that too low a coarse powder dosage (50 parts) leads to insufficient skeletal support, increased density, and increased settling amount, failing to achieve the desired overall effect within the preferred range of this invention.

[0089] Comparative Example 7 (without surface modification):

[0090] This comparative example is basically the same as Example 1, except that no surface modifier is added, that is, step (2) is directly omitted, and the rest is the same as Example 1.

[0091] Performance testing: density 2.08 g / cm³, thermal conductivity 1.43 W / m·K, viscosity 10800 mPa·s, 72h sedimentation 0.9 mm. The results indicate that the unmodified powder has poor compatibility with silicone oil, and the excessively high viscosity of the system severely affects flowability and is detrimental to potting operations.

[0092] Summary of performance of each embodiment and comparative example

[0093]

[0094] Results analysis and discussion:

[0095] As can be seen from the performance data of the above embodiments and comparative examples:

[0096] This invention achieves an excellent balance of low density, low sedimentation, suitable viscosity, and high thermal conductivity by combining a specific four-particle size distribution (70-80μm / 50-70μm / 7-10μm / 2-3μm) with a three-material compound of aluminum hydroxide, silicon dioxide, and alumina. The density of Example 1 (2.02 g / cm³) is significantly lower than that of Comparative Example 1 (pure alumina, 2.51 g / cm³) and Comparative Example 4 (commercially available product, 2.47 g / cm³), demonstrating a significant weight reduction effect; at the same time, the sedimentation (0.3 mm) is much lower than that of the comparative examples, exhibiting excellent anti-settling performance.

[0097] Particle size distribution is a key influencing factor. Comparative Example 5 changed the particle size range (without using the large-particle coarse powder of the present invention), and even with the same material, the density increased and the sedimentation increased, indicating that the 70-80μm coarse powder selected in the present invention is crucial as the skeleton.

[0098] The material blending produces a synergistic effect. This invention blends low-density aluminum hydroxide and silica with high thermal conductivity alumina, achieving an optimal balance among density, thermal conductivity, viscosity, and sedimentation compared to individual filler systems (Comparative Examples 1 to 3). In particular, compared to Comparative Example 3 (pure aluminum hydroxide), this invention improves thermal conductivity while significantly reducing viscosity and further minimizing sedimentation.

[0099] Surface modification is indispensable. Comparative Example 7, which did not undergo dry modification, experienced a sharp increase in viscosity (10800 mPa·s), rendering it useless and proving the necessity of the dry modification step in this invention.

[0100] The amount of coarse powder used needs to be within a suitable range. In Comparative Example Six, the amount of 70-80μm coarse powder was reduced to 50 parts (far lower than the preferred 200-500 parts of this invention), the sedimentation amount increased from 0.3mm to 1.5mm, and the density increased from 2.02 to 2.35g / cm³, indicating that the dosage range defined in claim 2 of this invention has a significant optimization effect.

[0101] In summary, the lightweight, anti-settling silicone thermally conductive potting compound powder filler and its preparation method provided by this invention effectively solve the prominent problems of high specific gravity, easy settling, and poor flowability of potting compounds in the prior art. It has outstanding substantive features and significant progress, and is suitable for promotion and application in fields such as electronic packaging, new energy, and energy storage.

[0102] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler, characterized in that: The powder filler is made by mixing components containing the following particle size ranges and materials and then dry-modifying them with a surface modifier: 200-500 parts of 70-80 micrometer aluminum hydroxide; 100-400 parts of 50-70 micrometer silicon dioxide; 100-400 parts of 7-10 micrometer aluminum hydroxide; 200-500 parts of 2-3 micrometer ordinary alumina; and 1-20 parts of surface modifier.

2. The lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler according to claim 1, characterized in that: The surface modifier is one of a silane coupling agent, a titanate coupling agent, or an aluminate coupling agent.

3. The lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler according to claim 1, characterized in that: The composition of the powder filler and surface modifier is as follows: 250 parts of 70-80 micron aluminum hydroxide; 200 parts of 50-70 micron silica; 300 parts of 7-10 micron aluminum hydroxide; 250 parts of 2-3 micron ordinary alumina; and 8 parts of surface modifier.

4. The lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler according to claim 1, characterized in that: The composition of the powder filler and surface modifier is as follows: 400 parts of 70-80 micron aluminum hydroxide; 150 parts of 50-70 micron silica; 150 parts of 7-10 micron aluminum hydroxide; and 300 parts of 2-3 micron ordinary alumina. 12 parts of surface modifier.

5. A method for preparing a lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler according to any one of claims 1-4, characterized in that: Includes the following steps: (1) Add 70-80 micrometer aluminum hydroxide, 50-70 micrometer silicon dioxide, 7-10 micrometer aluminum hydroxide and 2-3 micrometer aluminum oxide to a high-speed mixer and stir to mix evenly to obtain powder filler A; (2) Add surface modifier to the powder filler A and continue stirring to carry out dry modification to obtain the lightweight anti-settling organosilicon thermally conductive potting compound powder filler.

6. The preparation method of a lightweight, anti-settling, organosilicon thermally conductive potting compound powder filler according to claim 5, characterized in that: In step (1), the stirring speed is 20-40 Hz / min and the stirring time is 1-5 minutes; in step (2), the stirring speed is 10-50 Hz / min and the stirring time is 2-8 minutes.

7. A silicone thermally conductive potting compound, characterized in that, It comprises vinyl silicone oil and the lightweight, anti-settling, thermally conductive silicone potting compound powder filler as described in any one of claims 1-5.

8. The silicone thermally conductive potting compound according to claim 7, characterized in that: It comprises 100 parts of 100cp vinyl silicone oil and 450 parts of the powder filler as described in claim 1.

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