Heat-conducting caulking composition and preparation method thereof

Abstract

The invention discloses a heat-conducting caulking composition, which is prepared from the following raw materials: silicone rubber master batch, a coupling agent, heat-conducting filler and a vulcanizing aid, the silicone rubber master batch comprises modified silicone oil and silicone rubber, and the weight ratio of the modified silicone oil to the silicone rubber is 1: (1-3). The heat-conducting joint filling composition is a soft solid product, can meet filling of super-large gaps without vertical flow, has a more stable state in filling of super-large gaps with the width larger than 3 cm and the height larger than 10 cm of a home decoration intelligent box and a junction box, has the heat conductivity coefficient of 0.5 W / m.K or above, meets the heat conduction requirement of the home decoration intelligent box, has long-term use stability at the temperature ranging from-50 DEG C to 150 DEG C, and is suitable for large-scale popularization and application. V0 flame resistance can be achieved, and the cable is convenient to disassemble during maintenance and can be repeatedly used.

Description

Technical Field

[0001] This invention relates to the field of polymer compound compositions, and more specifically to a thermally conductive sealant composition and its preparation method. Background Technology

[0002] With the advancement of electronic information technology, the demand for gap filling between smart boxes and junction boxes is increasing. Traditional thermally conductive sealant materials are mostly liquid or solid. Solid sealant materials have a fixed thickness, making them inconvenient to use for gaps of varying widths. Liquid sealant materials are not effective at filling vertical or excessively large gaps, are prone to sagging, and cannot maintain their shape. Furthermore, existing thermally conductive sealant materials have poor aging resistance, their thermal conductivity decreases under high-temperature operating environments, and they are prone to oil seepage. Therefore, it is crucial to develop a thermally conductive sealant composition that is oil-resistant, aging-resistant, and provides long-term stability.

[0003] Chinese invention patent application CN114806494A discloses a low-density, high-thermal-conductivity silicone sealant and its preparation method. By surface modification of inorganic fillers, its dispersibility is improved, thereby increasing the amount of filler added. This results in a sealant with low density and high thermal conductivity, good flame retardancy, and excellent high and low temperature resistance and weather resistance after curing. However, its thermal conductivity is not high. Chinese invention patent application CN111471306A discloses a thermally conductive silicone putty for filling thermal interfaces. It is solid and can be directly adhered to the thermal interfaces of electronic products, making it convenient to use. Its hardness can be adjusted by regulating the content of methyl vinyl silicone rubber and dimethyl silicone oil, but its high-temperature resistance is poor. Summary of the Invention

[0004] In order to develop a thermally conductive sealant composition that is resistant to oil seepage, aging, and long-term stability, the first aspect of the present invention provides a thermally conductive sealant composition, the raw materials of which include: silicone rubber masterbatch, coupling agent, thermally conductive filler, and vulcanization aid; the silicone rubber masterbatch includes modified silicone oil and silicone rubber, wherein the weight ratio of the modified silicone oil to silicone rubber is 1:(1-3).

[0005] In one embodiment, the silicone rubber masterbatch comprises modified silicone oil and silicone rubber, wherein the weight ratio of the modified silicone oil to the silicone rubber is 1:1.

[0006] In one embodiment, the raw materials for preparing the modified silicone oil include hydroxyl-terminated vinyl silicone oil, phenyltriethoxysilane, hydrogen-containing silicone oil, and a catalyst.

[0007] In one embodiment, the weight ratio of the hydroxyl-terminated vinyl silicone oil, phenyltriethoxysilane, and hydrogen-containing silicone oil is (1-2):(0.1-0.5):(0.05-0.3).

[0008] In one embodiment, the catalyst includes a tin catalyst and a platinum catalyst.

[0009] In one embodiment, the tin catalyst is stannous octoate.

[0010] In one embodiment, the viscosity of the hydroxyl-terminated vinyl silicone oil at 25°C is 50-10000 cP, and the vinyl content of the hydroxyl-terminated vinyl silicone oil is 0.5-10 wt%.

[0011] In one embodiment, the hydroxyl-terminated vinyl silicone oil has a viscosity of 50-1000 cP at 25°C, and the vinyl content of the hydroxyl-terminated vinyl silicone oil is 1-8 wt%.

[0012] In one embodiment, the hydrogen content of the hydrogen-containing silicone oil is 0.005-5 wt%.

[0013] In one embodiment, the hydrogen content of the hydrogen-containing silicone oil is 0.01-3 wt%.

[0014] In one embodiment, the viscosity-average molecular weight of the silicone rubber is 400,000 to 800,000.

[0015] In one embodiment, the viscosity-average molecular weight of the silicone rubber is 550,000 to 650,000.

[0016] In one embodiment, the coupling agent includes γ-(methacryloyloxy)propyltrimethoxysilane and octyltrimethoxysilane.

[0017] In one embodiment, the weight ratio of γ-(methacryloyloxy)propyltrimethoxysilane to octyltrimethoxysilane is (0.05-0.1):(0.2-0.3).

[0018] In one embodiment, the thermally conductive filler includes large-particle-size filler and small-particle-size filler, wherein the D50 particle size of the large-particle-size filler is ≥20μm and the D50 particle size of the small-particle-size filler is <20μm.

[0019] In one embodiment, the thermally conductive filler includes at least one of alumina, silicon oxide, aluminum hydroxide, or aluminum nitride.

[0020] In one embodiment, the alumina includes alumina 1 and alumina 2, wherein the D50 particle size of alumina 1 is <20μm and the D50 particle size of alumina 2 is ≥20μm.

[0021] In one embodiment, the D50 particle size of the silicon oxide is 0.5-20 μm.

[0022] In one embodiment, the D50 particle size of the aluminum hydroxide is 5-40 μm.

[0023] In one embodiment, the aluminum nitride has a D50 particle size of 0.5-70 μm.

[0024] In one embodiment, the vulcanization aid includes an inhibitor, a crosslinking agent, and a catalyst.

[0025] In one embodiment, the inhibitor is 1,3-divinyltetramethyldisiloxane.

[0026] In one embodiment, the crosslinking agent is a hydrogen-containing silicone oil; the hydrogen content of the hydrogen-containing silicone oil is 0.005-5 wt%; the hydrogen content of the hydrogen-containing silicone oil is 0.01-3 wt%.

[0027] In one embodiment, the catalyst is a platinum catalyst.

[0028] A second aspect of the present invention provides a method for preparing a thermally conductive sealant composition, comprising the following steps: Preparation of modified silicone oil; Preparation of silicone rubber masterbatch; Mix the silicone rubber masterbatch and coupling agent by stirring at 20-40 r / min for 10-30 min; Add small-particle-size fillers and stir to mix, then add large-particle-size fillers and stir to mix, controlling the material temperature to not exceed 25℃; add vulcanizing aids and stir to mix, controlling the material temperature to not exceed 25℃. Stir and heat to 100-140℃, then keep warm for 1-4 hours; Vacuum degassing is performed to lower the temperature to below 70°C, resulting in a thermally conductive sealant composition.

[0029] As one embodiment, the preparation method of the thermally conductive sealant composition includes the following steps: Preparation of modified silicone oil; Preparation of silicone rubber masterbatch; Mix the silicone rubber masterbatch and coupling agent by stirring at 20-40 r / min for 10-30 min; Add small-particle-size fillers and stir to mix, then add large-particle-size fillers and stir to mix, controlling the material temperature to not exceed 25℃; add inhibitors and stir to mix, add crosslinking agents and stir to mix, add catalysts and stir to mix, controlling the material temperature to not exceed 25℃; Stir and heat to 100-140℃, then keep warm for 1-4 hours; Vacuum degassing is performed to lower the temperature to below 70°C, resulting in a thermally conductive sealant composition.

[0030] As one embodiment, the method for preparing the modified silicone oil includes the following steps: Hydroxyl-terminated vinyl silicone oil, phenyltriethoxysilane, and hydrogen-containing silicone oil were mixed and stirred at room temperature. After evacuation, inert gas is introduced, a catalyst is added, and stirring continues to produce a rubber compound. Heat the rubber compound to 80-100℃, stir and keep it at that temperature for 1-2 hours, then continue to heat it to 110-130℃, stir and keep it at that temperature for 1-2 hours. Continue stirring under vacuum until the temperature drops below 70°C to obtain modified silicone oil.

[0031] As one embodiment, the method for preparing the modified silicone oil includes the following steps: Mix and stir hydroxyl-terminated vinyl silicone oil, phenyltriethoxysilane and hydrogen-containing silicone oil at room temperature for 20-40 minutes. After evacuation, inert gas is introduced to maintain a pressure of 0-0.05 MPa and a temperature of 30°C. Stannous octoate is added first and stirred for 5-15 minutes. Then, platinum catalyst is added and stirred for another 5-15 minutes to obtain the rubber compound. Heat the rubber compound to 80-100℃, stir and keep it at that temperature for 1-2 hours, then continue to heat it to 110-130℃, stir and keep it at that temperature for 1-2 hours. The vacuum was evacuated to -0.08 to -0.1 MPa and stirred continuously until the temperature dropped below 70°C, thus obtaining the modified silicone oil.

[0032] As one embodiment, the method for preparing the silicone rubber masterbatch includes the following steps: Mix silicone rubber and modified silicone oil, stirring at 20-40 rpm for 10 minutes; Heat to 80-140℃, stir at 20-40 r / min for 1-3 hours, then turn off the heating. Vacuum degassing at 10-20 r / min (vacuum degree of -0.08 ~ -0.1 MPa) for 30-60 min, then cool and set aside for use.

[0033] Compared with the prior art, the present invention has the following beneficial effects: (1) The thermally conductive sealant composition of the present invention uses modified silicone oil prepared by hydroxyl-terminated vinyl silicone oil, phenyltriethoxysilane, hydrogen-containing silicone oil and catalyst, which can soften silicone rubber and has better oil resistance after cross-linking reaction. At the same time, the introduction of phenyl groups further improves the temperature resistance, oil resistance and stiffness of the rubber compound, giving the rubber compound large-size anti-sagging performance.

[0034] (2) The thermally conductive sealant composition of the present invention has a certain degree of crosslinking after the modified silicone oil is prepared, but still retains the form of liquid silicone oil, which can be better mixed with thermally conductive filler to achieve a higher thermal conductivity. At the same time, it retains a certain vinyl content, and the modified silicone oil and the macromolecular silicone rubber form a greater degree of crosslinking again, which further improves the product's oil resistance, aging resistance and large-size anti-sagging performance.

[0035] (3) The thermally conductive sealant composition of the present invention is prepared by first mixing modified silicone oil and silicone rubber to form silicone rubber masterbatch, and then preparing thermally conductive sealant composition, which improves the dispersion compatibility of silicone oil and silicone rubber.

[0036] (4) The preparation method of the thermally conductive sealant composition of the present invention involves first mixing the coupling agent with modified silicone oil and silicone rubber masterbatch, then adding the thermally conductive filler, and treating the filler during the production heating process. This method improves production efficiency, simplifies production steps, reduces environmental pollution, and saves costs while still achieving good treatment results. Compared with the existing technologies where wet processing is not suitable for industrial application and dry processing causes dust pollution, this application represents a substantial improvement.

[0037] (5) The preparation method of the thermally conductive sealant composition of the present invention first mixes fine-particle-size filler and then mixes coarse-particle-size filler, which can make the filler better dispersed in the colloid. The temperature of the rubber compound is controlled to be below 25°C. The inhibitor in the vulcanizing agent is added first and mixed evenly, then the vulcanizing agent is added and mixed evenly, and then the catalyst is added and mixed evenly. Under these conditions and the order of addition, the designed formula does not react at the beginning, but only begins to react as the temperature rises after heating. This makes the transportation and storage state more stable, improves production efficiency, and saves time and costs.

[0038] (6) The thermally conductive sealant composition of the present invention is a soft solid product that can fill ultra-large gaps without dripping. It has a more stable state in filling ultra-large gaps of more than 3cm wide and 10cm high in home decoration smart boxes and junction boxes. Such a large size will not drip during construction. At present, conventional products are either flowable or non-flowable liquid viscous products, which cannot achieve the effect of no dripping at this height and width.

[0039] (7) The thermal conductivity of the thermally conductive sealant composition of the present invention is above 0.5 W / m·K, which meets the thermal conductivity requirements of smart boxes for home decoration. It has long-term stability in use from -50℃ to 150℃ and can achieve V0 flame retardancy. It is also easy to use, does not require special tools, and can be done by hand. It has strong adaptability in the home decoration process. It is also easy to disassemble when the smart box for home decoration is damaged and can even be reused.

[0040] (8) The thermally conductive sealant composition of the present invention uses a combination of silicone rubber masterbatch and modified silicone oil mixed with thermally conductive filler. The overall reaction forms a network structure, which will not affect the state of the wall, thereby achieving the effect of long-term use and avoiding the problem that traditional thermally conductive sealant compositions dry out and lose their thermal conductivity after contacting the wall. Detailed Implementation

[0041] Examples and Comparative Examples A thermally conductive sealant composition is prepared from raw materials listed in Table 1, by weight.

[0042] Table 1

[0043] The hydroxyl-terminated vinyl silicone oil has a viscosity of 10-1000 cP at 25°C and a vinyl content of 1-8 wt%. It was purchased from Shenzhen Tianqi New Materials Technology Co., Ltd. and its brand name is SK-SOVOH-20.

[0044] The hydrogen-containing silicone oil has a hydrogen content of 0.01-3 wt%, is purchased from Shanghai Jingri New Materials Technology Co., Ltd., and its grade is H020.

[0045] The vinyl silicone oil has a viscosity of 50-1000 cP at 25°C and a vinyl content of 1-8 wt%. It was purchased from Dongguan Times Silicon Industry Co., Ltd. and its brand name is TVF-100.

[0046] The methyl silicone oil has a viscosity of 500 cP at 25°C and was purchased from Dow Chemical with the brand name PMX-200.

[0047] The silicone rubber has a viscosity-average molecular weight of 550,000-650,000 and was purchased from Jiangxi Lanxing Xinghuo Organosilicon Co., Ltd., with the grade 110-2.

[0048] The alumina 1 has a D50 particle size of <20μm and was purchased from Zhejiang Huafeng Electronic Substrate Co., Ltd., with the grade LDQA-01.

[0049] The alumina 2 has a D50 particle size ≥20μm and was purchased from Zhejiang Huafeng Electronic Substrate Co., Ltd., with the grade LDQA-45.

[0050] The silicon oxide has a D50 particle size of 0.5-20μm and was purchased from Zhejiang Huafeng Electronic Substrate Co., Ltd., with the grade SS-N10.

[0051] The aluminum hydroxide has a D50 particle size of 5-40 μm and was purchased from Zhejiang Xusen Flame Retardant Co., Ltd., with the brand name XS-ACW-10.

[0052] The aluminum nitride with a D50 particle size of 0.5-70 μm was purchased from Chengdu Xuci New Materials Co., Ltd., and its grade was TLA30.

[0053] The inhibitor is 1,3-divinyltetramethyldisiloxane.

[0054] The crosslinking agent is a hydrogen-containing silicone oil with a hydrogen content of 0.01-3 wt%, purchased from Shanghai Jingri New Materials Technology Co., Ltd., and its brand name is H020.

[0055] The catalyst is a platinum catalyst.

[0056] A method for preparing a thermally conductive sealant composition includes the following steps: Preparation of modified silicone oil; Preparation of silicone rubber masterbatch; Mix the silicone rubber masterbatch and coupling agent by stirring at 30 r / min for 20 min; Add small-particle-size filler and stir at 30 r / min for 20 min. Then add large-particle-size filler and stir at 30 r / min for 20 min, controlling the material temperature to not exceed 25℃. Add inhibitor and stir at 30 r / min for 20 min. Add crosslinking agent and stir at 30 r / min for 20 min. Add catalyst and stir at 30 r / min for 20 min, controlling the material temperature to not exceed 25℃. Stir at 30 r / min to raise the temperature to 125℃ and keep at that temperature for 2.5 h; Vacuum degassing at 15 r / min (vacuum degree of -0.09 MPa) for 45 min, allowing the temperature to drop below 70°C, yields a thermally conductive sealant composition.

[0057] The method for preparing the modified silicone oil includes the following steps: Hydroxyl-terminated vinyl silicone oil, phenyltriethoxysilane and hydrogen-containing silicone oil were mixed and stirred at room temperature for 30 min. After evacuation, inert gas is introduced to maintain a pressure of 0.03 MPa and a temperature of 30°C. Stannous octoate is added first and stirred for 10 minutes. Then, platinum catalyst is added and stirred for another 10 minutes to obtain the rubber compound. Heat the rubber compound to 90°C, stir and keep it at that temperature for 1.5 hours, then continue to heat it to 120°C, stir and keep it at that temperature for 1.5 hours. The vacuum was evacuated to -0.09 MPa and stirred continuously until the temperature dropped below 70°C, thus obtaining the modified silicone oil.

[0058] The preparation method of the silicone rubber masterbatch includes the following steps: Mix silicone rubber and modified silicone oil at a weight ratio of 1:1 and stir at 30 r / min for 10 min. Heat to 110℃, stir at 30r / min for 2 hours, then turn off the heating. Vacuum degassing at 15 r / min (vacuum degree of -0.09 MPa) for 45 min, then cool and set aside for use.

[0059] Performance testing 1. Thermal conductivity: Thermal conductivity of the tested examples and comparative examples was determined according to ASTM D5470 standard.

[0060] 2. Maximum torque: According to ASTM D5289 standard, the vulcanization curve was tested using a rotorless vulcanizer at 150℃ for 15 minutes to obtain MH, which is the maximum torque.

[0061] 3.150℃, 1000h aging thermal conductivity retention rate: First, the room temperature thermal conductivity of the thermally conductive sealant compositions of the examples and comparative examples was tested. Then, they were placed in an environment of 150℃ and aged for 1000h. The aging thermal conductivity was measured. Retention rate = (aging thermal conductivity / room temperature thermal conductivity) × 100%.

[0062] 4. Oil seepage ratio: The thermally conductive sealant compositions prepared in the examples and comparative examples are pressed into 2mm thick sheets, cut into circular pieces with a 2.5cm diameter circular cutter, placed on A4 paper, and placed in an oven at 150℃ for 24 hours. The diameter of the seeping oil stains is measured as a ratio to the original diameter.

[0063] 5. Flame retardancy rating: Flame retardancy performance of the examples and comparative examples was tested according to UL-94 standard.

[0064] 6. State and Workability: Take 20-50g of the thermally conductive sealant composition from the examples and comparative examples, and knead it by hand for 30 seconds. Observe the resistance: If it is easy to knead, readily forms a ball, and is not sticky, indicating good plasticity, the adhesive is soft; if it is difficult to knead and easily crumbles, it is relatively dry and hard, indicating poor plasticity; if the adhesive sticks to your hands while kneading, it is sticky. After kneading, lightly press the adhesive onto a vertical PVC board. If the adhesive adheres easily and does not fall off, and its shape remains unchanged, the adhesive is easy to apply; if it does not adhere to the PVC board or its shape changes after adhering to the PVC board, it is difficult to apply.

[0065] The test results are shown in Table 2.

[0066] Table 2

[0067] Aluminum nitride was added to the thermally conductive sealant composition prepared in Example 3, which enabled it to achieve a thermal conductivity of over 6 W / m·K.

[0068] Comparative Example 1 uses conventional methyl silicone oil instead of modified silicone oil, without vulcanization system, and is a non-curing product. Its rubber compound is significantly thinner and cannot achieve large-size anti-sagging effect. Its aging resistance and oil penetration resistance are significantly worse.

[0069] Comparative Example 2 uses vinyl silicone oil instead of modified silicone oil, matching the vulcanization system. It is a curing product with significantly higher torque, significantly harder adhesive, and cannot adhere to vertical junction boxes. Its aging resistance is also significantly worse, and its oil penetration resistance is not as good as that of Example 2.

[0070] Comparative Example 3 uses methyl silicone oil and vinyl silicone oil together with the same curing system as in Example 2. This is a cured product. This situation is closest to the effect of the example formulation. Although the state is similar, the oil penetration resistance and aging resistance are significantly worse.

Claims

1. A thermally conductive caulk composition characterized by, The preparation raw materials include: silicone rubber masterbatch, coupling agent, heat-conducting filler, vulcanization aid; the silicone rubber masterbatch includes modified silicone oil and silicone rubber, and the weight ratio of the modified silicone oil to the silicone rubber is 1: (1-3).

2. The thermally conductive caulk composition of claim 1, wherein, The preparation raw materials of the modified silicone oil include end-hydroxyl vinyl silicone oil, phenyl triethoxysilane, hydrogen-containing silicone oil and catalyst.

3. The thermally conductive caulk composition of claim 2, wherein, The weight ratio of the end-hydroxyl vinyl silicone oil, the phenyl triethoxysilane and the hydrogen-containing silicone oil is (1-2): (0.1-0.5): (0.05-0.3).

4. The thermally conductive caulk composition of claim 2, wherein, The viscosity of the end-hydroxyl vinyl silicone oil at 25℃ is 50-10000 cP, and the vinyl content of the end-hydroxyl vinyl silicone oil is 0.5-10 wt%.

5. The thermally conductive caulk composition of claim 2, wherein, The hydrogen content of the hydrogen-containing silicone oil is 0.005-5 wt%.

6. The thermally conductive caulk composition of claim 1, wherein, The viscosity-average molecular weight of the silicone rubber is 400-800 thousand.

7. The thermally conductive caulk composition of claim 2, wherein, The heat-conducting filler includes large-particle-size filler and small-particle-size filler, the D50 particle size of the large-particle-size filler is ≥20 μm, and the D50 particle size of the small-particle-size filler is <20 μm.

8. The thermally conductive caulk composition of claim 7, wherein, The heat-conducting filler includes at least one of aluminum oxide, silicon oxide, aluminum hydroxide or aluminum nitride.

9. A process for the preparation of a heat-conducting caulk composition according to claims 7-8, characterized in that, The method includes the following steps: Preparation of modified silicone oil; Preparation of silicone rubber masterbatch; Mixing the silicone rubber masterbatch and the coupling agent at 20-40 r / min for 10-30 min; Adding the small-particle-size filler, stirring and mixing, then adding the large-particle-size filler, stirring and mixing, and controlling the material temperature to be not more than 25℃; adding the vulcanization aid, stirring and mixing, and controlling the material temperature to be not more than 25℃; Raising the temperature to 100-140℃ and keeping the temperature for 1-4 h; Vacuum degassing, and lowering the temperature to be lower than 70℃ to obtain the heat-conducting joint composition.

10. The method of claim 9, wherein, The preparation method of the modified silicone oil includes the following steps: Mixing and stirring the end-hydroxyl vinyl silicone oil, the phenyl triethoxysilane and the hydrogen-containing silicone oil at room temperature; After vacuumizing, introducing inert gas, adding catalyst and continuing to stir to obtain the rubber compound; Raising the temperature of the rubber compound to 80-100℃, stirring and keeping the temperature for 1-2 h, continuing to raise the temperature to 110-130℃, stirring and keeping the temperature for 1-2 h; Vacuumizing and continuing to stir, and lowering the temperature to be lower than 70℃ to obtain the modified silicone oil.

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