Ageing-resistant high-thermal-conductivity organic silicon gasket filler as well as preparation method and application thereof

Abstract

The invention relates to the technical field of heat-conducting materials, and particularly discloses an anti-aging high-heat-conductivity organic silicon gasket filler as well as a preparation method and application thereof. The composition comprises powder filler with specific particle size grading (400-650 parts of aluminum oxide with the particle size of 50-70 microns, 100-350 parts of aluminum oxide with the particle size of 5-7 microns, 100-350 parts of aluminum oxide with the particle size of 1-3 microns and 0-250 parts of aluminum hydroxide with the particle size of 40-70 microns) and a synergistic surface modifier (A / B is a silane coupling agent, and C is silicone oil). A continuous heat conduction network is constructed through aluminum oxide with three-level particle sizes, so that the heat conductivity coefficient reaches 5.0-6.0 W / (m.K); aluminum hydroxide is added as required to realize flexible balance between flame retardance (V0 level) and high thermal conductivity; the three modifiers synergistically inhibit thermo-oxidative aging, the heat conduction attenuation after aging at 150 DEG C for 500 h is smaller than or equal to 0.3 W / (m.K), and the hardness change is smaller than or equal to Shore 0020. During preparation, a three-step stirring process is adopted, the powder is firstly mixed, and then the modifier is added step by step or synchronously. The composition is suitable for electronic heat dissipation gaskets of a new energy automobile battery module and the like, and has the advantages of high heat conductivity, aging resistance and low cost.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of silicone gasket fillers, in particular to a high-thermal-conductivity silicone gasket filler with aging resistance, and a preparation method and application thereof. BACKGROUND

[0002] With the continuous increase of power density of electronic equipment, as a key heat dissipation material, the silicone thermal conductive gasket has higher requirements for its thermal conductivity, long-term aging resistance and cost controllability. Currently, high-thermal-conductivity silicone gasket technology is mainly realized by optimizing the composite of silicone matrix and thermal conductive filler, but there are still the following core defects:

[0003] The traditional filler (such as single-particle-size aluminum oxide) has low bulk density and discontinuous thermal conduction path, and the thermal conductivity coefficient is difficult to break through 3.0 W / (m·K);

[0004] The silicone matrix is prone to thermal oxidative aging (silicon-oxygen bond rupture) at high temperature, resulting in rising hardness and decay of thermal conductivity;

[0005] High-thermal-conductivity fillers (such as boron nitride, carbon nanotubes) are expensive and have complex compounding processes, making it difficult to balance high thermal conductivity and low-cost mass production.

[0006] The prior art attempts to improve performance by filler compounding, but there are still limitations. Chinese Invention Patent CN 117343546A discloses a high-thermal-conductivity low-specific-gravity silicone composition, which uses aluminum hydroxide as the main filler (accounting for ≥55%) and combines double-particle-size grading (0.1–2 μm and 10–40 μm) to reduce density. However, this scheme has obvious deficiencies:

[0007] The thermal conductivity is limited, as the thermal conductivity of aluminum hydroxide is much lower than that of aluminum oxide, and its thermal conductivity coefficient is only up to 3.97 W / (m·K), which cannot meet the needs of high-temperature scenarios such as 5G communication and new energy vehicle batteries; the aging resistance is ignored, and the performance decay problem under long-term use at high temperature is not solved, and there is a lack of aging test data support. SUMMARY

[0008] The purpose of the present application is to provide a silicone gasket filler composition with high thermal conductivity, excellent aging resistance and low-cost mass production capability.

[0009] In order to achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0010] A high-thermal-conductivity silicone gasket filler composition with aging resistance, comprising a powder filler and a surface modifier; the powder filler is composed of the following components by weight parts:

[0011] Aluminum oxide with a particle size of 50–70 μm: 400–650 parts;

[0012] alumina with a particle size of 5-7 μm: 100-350 parts;

[0013] alumina with a particle size of 1-3 μm: 100-350 parts;

[0014] alumina with a particle size of 40-70 μm: 0-250 parts;

[0015] The surface modifier comprises:

[0016] Surface modifier A: at least one selected from the group consisting of an amino silane coupling agent, an epoxy silane coupling agent, a mercapto silane coupling agent, a vinyl silane coupling agent, a methacryloxy silane coupling agent, a long-chain alkyl silane, and a non-reactive silane;

[0017] Surface modifier B: at least one selected from the group consisting of an amino silane coupling agent, an epoxy silane coupling agent, a mercapto silane coupling agent, a vinyl silane coupling agent, and a methacryloxy silane coupling agent;

[0018] Surface modifier C: at least one selected from the group consisting of a silicone oil, a modified silicone oil, and a polyether-modified siloxane.

[0019] Further, the surface modifier is added in an amount of:

[0020] Surface modifier A: 1-10 parts by weight;

[0021] Surface modifier B: 1-10 parts by weight;

[0022] Surface modifier C: 2-5 parts by weight.

[0023] Further, the composition ratio of the powder filler is:

[0024] alumina with a particle size of 50-70 μm: alumina with a particle size of 5-7 μm: alumina with a particle size of 1-3 μm: alumina with a particle size of 40-70 μm = (400-650):(100-350):(100-350):(0-250).

[0025] Further, when the composition is filled with 1700-2000 parts of silicone oil per 100 parts, the thermal conductivity is 5.0-6.0 W / (m·K), and after aging at 150°C for 500 hours:

[0026] The thermal conductivity decreases by ≤0.3 W / (m·K);

[0027] The hardness changes by ≤Shore 0020.

[0028] A method for preparing an aging-resistant high-thermal-conductivity silicone gasket filler composition, comprising the following steps:

[0029] (1) The particle size of 40-70 mu m aluminum hydroxide, 50-70 mu m aluminum oxide, 5-7 mu m aluminum oxide, 1-3 mu m aluminum oxide is stirred at 300-1200 revolutions per minute for 1-3 minutes to obtain powder filler A;

[0030] (2) The powder filler A, surface modifier A and surface modifier B are stirred at 1000-3000 revolutions per minute for 3-10 minutes to obtain powder filler B;

[0031] (3) The powder filler B and surface modifier C are stirred at 1000-2000 revolutions per minute for 3-10 minutes to obtain the filler composition.

[0032] Further, the surface modifier A and the surface modifier B are added simultaneously in step (2).

[0033] Further, the surface modifier A is added and stirred first, and then the surface modifier B is added and stirred in step (2).

[0034] The application of the aging-resistant high-thermal-conductivity silicone gasket filler composition in electronic heat dissipation gaskets for mobile phones, notebook computers or new energy automobile battery modules.

[0035] The beneficial effects of the application are:

[0036] The aging-resistant high-thermal-conductivity silicone gasket filler composition provided by the application realizes the following beneficial effects through the synergistic effect of the specific particle size compounded aluminum oxide main filler, the flexible and controllable aluminum hydroxide auxiliary filler and the three types of surface modifiers:

[0037] (1) The application takes 50-70 mu m aluminum oxide as the "thermal conduction framework" to build the basic heat transfer network, and then fills the gaps between the large particle size framework through 5-7 mu m and 1-3 mu m aluminum oxide to form a "skeleton, filling" close packing structure, which greatly reduces the gap hindrance in the heat transfer process; taking 100 parts of silicone oil as the reference (mass ratio), 1700-2000 parts of filler are filled, which further improves the proportion of the filler in the system, so that the filler particles fully contact to form a continuous heat conduction channel, and reduces the weakening of the low thermal conductivity silicone oil on heat transfer; through the above synergistic effect, the thermal conductivity of the composition can reach 5.0-6.0 W / (m·K), realizing excellent high-thermal-conductivity performance.

[0038] (2) The application can realize the precise balance of flame retardancy, rubber viscosity and structural performance under different thermal conductivity requirements by adjusting the addition amount of aluminum hydroxide:

[0039] When the thermal conductivity is at 3-4 W / (m·K): a small amount of aluminum hydroxide (less than 10%) can reduce the viscosity of the rubber compound, improve processability, and at the same time improve the structural performance of the sheet, such as compactness and mechanical stability; a large amount of aluminum hydroxide (more than 10%, such as 100-250 parts added to 100 parts of silicone oil): not only can achieve UL94 V0 level flame retardation, but also can further improve the thermal conductivity, and meet the requirements of flame retardation and thermal conductivity.

[0040] When the thermal conductivity is at 5-6 W / (m·K): without adding aluminum hydroxide, relying on the high filling and component synergy of the system, UL94 V0 level flame retardation effect can be achieved, and at the same time, when the amount of aluminum hydroxide is 0 parts, the viscosity of the rubber compound is the lowest and the gasket structural performance is the best.

[0041] (3) The application uses aluminum oxide and aluminum hydroxide as the main heat-conducting material, which significantly reduces the cost of raw materials compared to high-valence heat-conducting filler systems such as boron nitride; at the same time, relying on the flexible addition range of 0-250 parts of aluminum hydroxide, the performance requirements of different scenarios can be precisely adapted; for example, in scenarios such as new energy vehicle battery modules that require high flame retardation and focus on cost control, by adjusting the amount of aluminum hydroxide, both functional requirements and economy can be met, showing strong scenario adaptability. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the application will be described below in a clear and complete manner. Obviously, the described embodiments are only part of the embodiments of the application, not all embodiments. Based on the embodiments in the application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the application.

[0043] The filler composition of the application comprises the following components (by weight):

[0044] Powder filler:

[0045] 50-70 μm aluminum oxide: 400-650 parts (preferably spherical alpha-alumina, purity ≥ 99%);

[0046] 5-7 μm aluminum oxide: 100-350 parts (spherical alpha-alumina);

[0047] 1-3 μm aluminum oxide: 100-350 parts (ordinary alpha-alumina);

[0048] 40-70 μm aluminum hydroxide: 0-250 parts (flame-retardant grade, loss on ignition ≤ 34%);

[0049] Surface modifier:

[0050] Modifier A: 1-10 parts (may be selected from: aminopropyl triethoxysilane (KH550), 3-glycidoxypropyltrimethoxysilane (KH560), vinyltrimethoxysilane (A171), long-chain alkyl silane (such as octadecyltrimethoxysilane), non-reactive silane (such as methyltrimethoxysilane), γ-aminopropyl triethoxysilane (KH550))

[0051] Modifier B: 1-10 parts (selected from: methacryloxypropyltrimethoxysilane (KH570), mercaptopropyltrimethoxysilane, vinylsilane (A151), or mercaptosilane (KH590))

[0052] Modifier C: 2-5 parts (selected from: dimethyl silicone oil (500 cP), polyether-modified siloxane, methyl silicone oil (100 cP), polyether-modified siloxane).

[0053] Preparation method example

[0054] Example 1 (simultaneous addition of modifiers A / B)

[0055] Pre-mixed powder: 50-70 μm alumina (600 parts), 5-7 μm alumina (250 parts), 1-3 μm alumina (150 parts), aluminum hydroxide (0 parts) are added to a high-speed mixer, stirred at 300 rpm for 3 minutes, to obtain powder A.

[0056] Surface modification treatment: KH560 (modifier A, 5 parts) and KH570 (modifier B, 5 parts) are added to powder A, stirred at 1000 rpm for 10 minutes, to obtain powder B.

[0057] Final treatment: powder B is stirred with dimethyl silicone oil (modifier C, 3 parts) at 1000 rpm for 10 minutes, to obtain the finished product.

[0058] Example 2 (containing flame-retardant function)

[0059] Step 1: 50-70 μm alumina (400 parts), 5-7 μm alumina (250 parts), 1-3 μm alumina (150 parts), aluminum hydroxide (200 parts) are stirred at 1200 rpm for 1 minute, to obtain powder A;

[0060] Step 2: powder A + A171 (modifier A, 1 part) + mercaptopropyltrimethoxysilane (modifier B, 10 parts) are stirred at 3000 rpm for 3 minutes, to obtain powder B;

[0061] Step 3: powder B + polyether-modified siloxane (modifier C, 5 parts) are stirred at 2000 rpm for 3 minutes, to obtain the finished product.

[0062] Example 3 (stepwise addition of modifiers)

[0063] Step 1 same as Example 1;

[0064] Step 2 changed to: first add KH550 (modifier A, 8 parts) and stir at 3000 rpm for 3 minutes; then add A171 (modifier B, 2 parts) and stir at 3000 rpm for 7 minutes, to obtain powder B;

[0065] Step 3 same as Example 1.

[0066] Performance test and effect verification

[0067] The filler composition of Example was added to 100 parts of silicone oil to make a 2mm gasket for testing:

[0068]

[0069] High thermal conductivity: when the ratio of silicone oil to filler reaches 1:20, and the amount of aluminum hydroxide is 0 parts, the thermal conductivity reaches 5.98 W / (m·K);

[0070] Thermal conductivity attenuation after aging ≤0.23 W / (m·K) (much lower than ≤0.3 W / (m·K)).

[0071] Note: Thermal conductivity attenuation value = initial thermal conductivity - thermal conductivity after aging.

[0072] Flame retardance and thermal conductivity balance: when adding aluminum hydroxide (Example 2); the effect on thermal conductivity is small; but UL94 V0 flame retardance is achieved at the same time, meeting the needs of battery module and other scenarios.

[0073] Aging resistance: the hardness change of all examples after aging is ≤Shore 0016, and the hardness change is related to the modification process:

[0074] Adding modifier A / B (Example 1) simultaneously changes + Shore 009;

[0075] Step-by-step addition (Example 3) changes + Shore 0016, still meets the requirements but is slightly inferior.

[0076] Example 3 proves the feasibility of step-by-step addition of modifiers, although the performance is slightly lower but meets the basic requirements.

[0077] Application example

[0078] The filler composition of Example 1 is applied to the following scenarios:

[0079] New energy vehicle battery module:

[0080] In 100 parts of silicone oil, 2000 parts of filler are filled to make a 2mm thick gasket. After 1000 times of high temperature cycle test (-40℃~150℃), the thermal conductivity remains 5.73W / (m·K), and the flame retardancy passes GB / T2408 V0 level.

[0081] 5G base station chip heat dissipation:

[0082] The thermal conductivity remains 4.95W / (m·K), and the long-term work can reduce the chip working temperature by 18℃.

[0083] The application solves the continuity problem of the heat conduction network by specific particle size grading:

[0084] 50-70μm alumina (accounting for ≥60% of the total) forms a rigid skeleton, and the lower limit of the particle size is 50μm to ensure the compressive strength of the skeleton (>10MPa), and the upper limit is 70μm to control the void ratio <35%;

[0085] 5-7μm alumina fills the 10-20μm macroscopic gap between the skeleton, and the particle size and gap size matching degree is >90%;

[0086] 1-3μm alumina further seals ≤5μm microcracks, and the particle size >3μm cannot enter the microcracks (see Comparative Example 3);

[0087] 40-70μm aluminum hydroxide decomposes and absorbs heat in the flame retardant scene, and when the particle size is <40μm, the decomposition rate is too fast (TGA shows that the weight loss is >80% in 5min), which leads to insufficient flame retardant aging.

[0088]

[0089] Particle size-function correlation experiment verification (other conditions are fixed):

[0090] Filler addition amount reference: relative to 100 parts of silicone oil

[0091] Example 1 fills 2000 parts

[0092] Comparative Example 1 fills 2000 parts

[0093] Comparative Example 2 fills 2000 parts

[0094] Comparative Example 3 fills 2000 parts

[0095] Example 2 fills 1000 parts

[0096] Comparative Example 4 fills 1000 parts

[0097]

[0098] Based on the systematic particle size-function correlation experiment, the present technology concludes the following:

[0099] Three-level particle size synergy mechanism is indispensable:

[0100] Large particle size alumina (50-70 μm) as a rigid skeleton to build the dominant thermal network, providing more than 60% of the heat conduction path;

[0101] Medium particle size alumina (5-7 μm) precisely fills 10-20 μm macroscopic voids, and improves the packing density of the filler to >92%;

[0102] Fine particle size alumina (1-3 μm) is critical to seal ≤5 μm microcracks, eliminating local thermal resistance points - the three synergies make the thermal conductivity break through 5.98 W / (m·K).

[0103] Fine particle size golden interval verification:

[0104] Through comparative experiments, it is found that the 1-3 μm particle size shows significant gradient difference in microcrack sealing effect:

[0105] 1-2 μm is the optimal interval, which can completely penetrate microcracks and achieve a thermal conductivity of >5.5 W / (m·K);

[0106] 2-3 μm is still effective but the efficiency is reduced, as the particle size approaches the upper limit of the microcrack, resulting in a decrease in filling rate of about 8%;

[0107] >3 μm (such as 8 μm) cannot enter the microcrack (matching degree <30%), and the thermal conductivity drops by 31% to 4.12 W / (m·K);

[0108] Although <1 μm can fill microcracks, it significantly increases the viscosity of the system (>50,000 cP), resulting in poor processing performance.

[0109] Conclusion: In Comparative Example 3, the fine particle size is increased to 8 μm, and the thermal conduction network appears "thermal conduction path discontinuity / local thermal resistance point", and the actual thermal conductivity decreases by 31% (5.98→4.12 W / (m·K)), which proves that 1-3 μm is the irreplaceable key particle size range to maintain high thermal conductivity.

[0110] Example 4

[0111] Powder formulation:

[0112] 50-70 μm alumina: 400 parts (particle size 50 μm critical)

[0113] 5-7 μm alumina: 100 parts (particle size 7 μm critical)

[0114] 1-3 μm alumina: 100 parts (particle size 3 μm critical)

[0115] Aluminum hydroxide: 250 parts (particle size 70 μm critical)

[0116] Performance: 100 parts of silicone oil filled 1000 parts of filler, thermal conductivity 3.02 W / (m·K) (containing aluminum hydroxide), flame retardant V0 level, hardness change Shore 009 after aging.

[0117] The above-described embodiments are only preferred embodiments of the present application, and it should be pointed out that for ordinary skilled in the art, without departing from the technical principles of the present application, a number of improvements and replacements can be made, and these improvements and replacements should be considered as the protection scope of the present application.

Claims

1. An aging-resistant and highly thermally conductive silicone gasket filler composition, characterized by: Contains powder filler and surface modifier; the powder filler is composed of the following components by weight: Alumina with a particle size of 50–70 μm: 400–650 parts; Alumina with a particle size of 5–7 μm: 100–350 parts; Alumina with a particle size of 1–3 μm: 100–350 parts; Aluminum hydroxide with a particle size of 40–70 μm: 0–250 parts; The surface modifier includes: Surface modifier A: at least one selected from aminosilane coupling agent, epoxysilane coupling agent, mercaptosilane coupling agent, vinylsilane coupling agent, methacryloxysilane coupling agent, long-chain alkylsilane, and non-reactive silane; Surface modifier B: at least one selected from aminosilane coupling agent, epoxysilane coupling agent, mercaptosilane coupling agent, vinylsilane coupling agent, and methacryloxysilane coupling agent; surface modifier C: at least one selected from silicone oil, modified silicone oil, and polyether modified siloxane.

2. The aging-resistant and highly thermally conductive organic silicone gasket filler composition according to claim 1, characterized in that: The addition amount of the surface modifier is: Surface modifier A: 1-10 parts by weight; Surface modifier B: 1-10 parts by weight; Surface modifier C: 2-5 parts by weight.

3. The aging-resistant and highly thermally conductive silicone gasket filler composition according to claim 1, characterized in that: The composition ratio of the powder filler is: Particle size 50–70 μm aluminum oxide: particle size 5–7 μm aluminum oxide: particle size 1–3 μm aluminum oxide: particle size 40–70 μm aluminum hydroxide = (400–650): (100–350): (100–350): (0–250).

4. The aging-resistant and highly thermally conductive silicone gasket filler composition according to claim 1, characterized in that: When the composition is filled with 1700-2000 parts of silicone oil in 100 parts of silicone oil, the thermal conductivity is 5.0-6.0 W / (m·K), and after aging at 150° C. for 500 hours: Thermal conductivity decreases ≤0.3W / (m·K); Hardness change ≤ Shore 0020.

5. A method for preparing the filler composition according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Aluminum hydroxide, aluminum oxide, aluminum oxide with a particle size of 40–70 μm, aluminum oxide with a particle size of 50–70 μm, aluminum oxide with a particle size of 5–7 μm, and aluminum oxide with a particle size of 1–3 μm were stirred at 300–1200 rpm for 1–3 minutes to obtain powder filler A; (2) stirring the powder filler A, the surface modifier A, and the surface modifier B at 1000-3000 rpm for 3-10 minutes to obtain the powder filler B; (3) Stirring the powder filler B and the surface modifier C at 1000-2000 rpm for 3-10 minutes to obtain the filler composition.

6. The method according to claim 5, characterized in that In step (2), the surface modifier A and the surface modifier B are added simultaneously.

7. The method according to claim 5, characterized in that In step (2), surface modifier A is first added and stirred, and then surface modifier B is added and stirred.

8. Use of the filler composition according to any one of claims 1 to 4 in an electronic heat dissipation gasket, characterized in that: The electronic heat dissipation gasket is used for mobile phones, laptop computers or new energy vehicle battery modules.

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