Thermally conductive silicone rubber and preparation method therefor

Abstract

The present invention relates to the technical field of thermally conductive silicone rubber, and in particular to thermally conductive silicone rubber and a preparation method therefor. The present invention provides thermally conductive silicone rubber and a preparation method therefor. The thermally conductive silicone rubber comprises: vinyl-terminated polydimethylsiloxane, vinyl MQ resin, hydrogen-containing silicone oil, ethynylcyclohexanol, and modified silver powder. The modified silver powder is a mixture containing a silicone resin and silver powder. The use of the silver powder coated with the silicone resin in the thermally conductive silicone rubber provided by the present invention enables the thermally conductive silicone rubber to exhibit suitable flowability before curing and a high thermal conductivity coefficient, and to meet use requirements for silicone rubber having ultra-high thermal conductivity on the market. The thermally conductive silicone rubber provided by the present invention can be applied to structural heat dissipation components such as ultra-high power light-emitting chips.

Description

A thermally conductive silicone rubber and its preparation method

[0001] Cross-reference to related applications

[0002] This invention claims priority to Chinese Patent Application No. 202411206803.2, filed on August 30, 2024, entitled "A thermally conductive silicone rubber and a method for preparing the same," the entire contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of thermally conductive silicone rubber technology, specifically to a thermally conductive silicone rubber and its preparation method. Background Technology

[0004] In existing technologies, thermally conductive silicone rubber generally uses polysiloxane as a base material and fills it with metal oxides as fillers. Currently, the thermal conductivity of thermally conductive silicone rubber is generally between 0.5 and 8 W / (m·K). With constantly changing market demands, the required thermal conductivity of thermally conductive silicone rubber is becoming increasingly stringent. To meet these demands, it is necessary to develop silicone rubber with higher thermal conductivity. Current research attempts to improve the thermal conductivity of silicone rubber by filling it with metal powders such as copper, silver, and nickel. However, due to the inherent properties of metal powders, adding metal powders to improve the thermal conductivity of thermally conductive silicone rubber can lead to insufficient flowability before curing, or excessively high viscosity. These factors make the preparation of thermally conductive silicone rubber difficult or limit its application areas.

[0005] Therefore, there is a need for a silicone rubber that has fluidity and high thermal conductivity before curing. Summary of the Invention

[0006] To address the aforementioned problems in the prior art, this invention proposes a thermally conductive silicone rubber and its preparation method.

[0007] In a first aspect, the present invention provides a thermally conductive silicone rubber comprising: vinyl-terminated polydimethylsiloxane, vinyl MQ resin, hydrogen-containing silicone oil, ethynylcyclohexanol, and modified silver powder; wherein the modified silver powder is a mixture containing silicone resin and silver powder.

[0008] As a specific embodiment of the present invention, at a temperature of 25°C and 0.2S -1 At a certain shear rate, the shear viscosity of the thermally conductive silicone rubber of the present invention is 60,000 to 100,000 mPa·s. For example, the viscosity of the thermally conductive silicone rubber can be 60,000 mPa·s, 70,000 mPa·s, 80,000 mPa·s, 90,000 mPa·s, 100,000 mPa·s, or a range thereof.

[0009] In this invention, the viscosity of the thermally conductive silicone rubber was tested using an Anton Paar MCR102 rheometer.

[0010] As a specific embodiment of the present invention, the thermal conductivity of the thermally conductive silicone rubber of the present invention is 10 to 18 W / (m·K). For example, the thermal conductivity of the thermally conductive silicone rubber can be 10 W / (m·K), 11 W / (m·K), 12 W / (m·K), 13 W / (m·K), 14 W / (m·K), 15 W / (m·K), 16 W / (m·K), 17 W / (m·K), 18 W / (m·K), or a range thereof.

[0011] In this invention, the transient planar heat source method is used to test the thermal conductivity of thermally conductive silicone rubber, and a Hot Disk TPS 500S thermal conductivity meter is used.

[0012] As a specific embodiment of the present invention, according to the GBT 2411-2008 standard, the hardness of the thermally conductive silicone rubber after curing is 50 to 95A. For example, the hardness of the thermally conductive silicone rubber after curing is 50A, 60A, 70A, 80A, 90A, 95A or a range thereof.

[0013] As a specific embodiment of the present invention, at a temperature of 25°C, the dynamic viscosity of the vinyl-terminated polydimethylsiloxane is 200–500,000 mPa·s. For example, the viscosity can be 200 mPa·s, 500 mPa·s, 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 3000 mPa·s, 4000 mPa·s, 5000 mPa·s, 6000 mPa·s, 7000 mPa·s, 8000 mPa·s, 9000 mPa·s, 10… The viscosity of the vinyl-terminated polydimethylsiloxane is within the range of 000 mPa·s, 15000 mPa·s, 20000 mPa·s, 25000 mPa·s, 30000 mPa·s, 35000 mPa·s, 40000 mPa·s, 45000 mPa·s, 50000 mPa·s, 100000 mPa·s, 200000 mPa·s, 300000 mPa·s, 400000 mPa·s, 500000 mPa·s, or a combination thereof, preferably 3000–20000 mPa·s. The viscosity of the vinyl-terminated polydimethylsiloxane was tested using a Brookfield DV2TRV viscometer.

[0014] In a specific embodiment of the present invention, the vinyl MQ resin has M units and Q units, wherein the M unit is R3SiO 1 / 2 The monofunctional siloxane unit shown has a Q unit of SiO. 4 / 2The tetrafunctional siloxane unit shown; in each M unit, the three substituents R are the same or different, and are each independently selected from hydrocarbon groups, preferably C1-C3 alkyl and C2-C5 alkenyl groups.

[0015] Examples of C1-C3 alkyl groups include, but are not limited to, methyl, ethyl, and propyl. Similarly, examples of C2-C5 alkenyl groups include, but are not limited to, vinyl and allyl.

[0016] In this invention, the R values ​​in different M units of vinyl MQ silicone resin can be the same or different, and vinyl MQ silicone resin includes M units containing vinyl groups.

[0017] In some embodiments, at a temperature of 25°C, the molar ratio of M units to Q units in the vinyl MQ silicone resin is 0.9 to 1.1, for example, the molar ratio of M units to Q units is 0.9, 0.95, 1, 1.1 or a range thereof.

[0018] In the vinyl MQ silicone resin of the present invention, the molar ratio of M units to Q units can generally be determined by the amount of feed. The molar ratio of M units to Q units can be obtained by calculating the amount of substance of the M monomer and the Q monomer. In this invention, the terms "M monomer" and "Q monomer" refer to the monomers that form the corresponding M units and Q units in the polymerization reaction.

[0019] For example, in the synthesis of vinyl MQ silicone resin using the tetraethyl orthosilicate method, the amount of monomer M is half the sum of the amounts of hexamethyldisiloxane and tetramethyldivinyldisiloxane, and the amount of monomer Q is the amount of tetraethyl orthosilicate.

[0020] As a specific embodiment of the present invention, the vinyl content of the vinyl MQ silicone resin is 0.0006 to 0.002 mol / g. For example, the vinyl content of the vinyl MQ silicone resin can be 0.0006 mol / g, 0.0008 mol / g, 0.001 mol / g, 0.0012 mol / g, 0.0015 mol / g, 0.0018 mol / g, 0.002 mol / g, or a range thereof.

[0021] The vinyl content in vinyl MQ silicone resin is generally determined based on the amount of raw materials used during synthesis. First, calculate the amount of vinyl in the vinyl-containing M monomer, then divide it by the total mass of the MQ silicone resin to obtain the vinyl content of the vinyl MQ silicone resin, expressed in mmol / g.

[0022] For example, in the synthesis of vinyl MQ silicone resin using the tetraethyl orthosilicate method, the vinyl content is calculated using hexamethyldisiloxane (x g), tetramethyldivinyldisiloxane (y g), and tetraethyl orthosilicate (z g) as follows: (y / 93) ÷ (x + y + z × 0.288), where 93 is half the molar mass of tetramethyldivinyldisiloxane, and 0.288 is the molar mass of SiO₂. 4 / 2 The mass fraction in tetraethyl orthosilicate is because the four ethoxy groups in tetraethyl orthosilicate will hydrolyze, and the Q-unit will only contain SiO. 4 / 2 .

[0023] In this invention, the vinyl content in vinyl MQ silicone resin can be measured using iodometric titration. Specifically, the method for measuring the vinyl content in vinyl MQ silicone resin includes: adding excess iodine bromide to the vinyl MQ silicone resin to allow the iodine bromide to undergo an addition reaction with the vinyl group; adding excess potassium iodide to react with unreacted potassium bromide to generate elemental iodine; titrating the elemental iodine with a standard sodium thiosulfate solution to calculate the vinyl content.

[0024] Specifically, the present invention may use vinyl MQ resin with CAS number 68988-89-6.

[0025] As a specific embodiment of the present invention, at a temperature of 25°C, the dynamic viscosity of the hydrogen-containing silicone oil is 10 to 200 mPa·s. For example, the viscosity can be 10 mPa·s, 50 mPa·s, 80 mPa·s, 100 mPa·s, 120 mPa·s, 150 mPa·s, 180 mPa·s, 200 mPa·s or a range thereof, preferably 15 to 50 mPa·s.

[0026] The viscosity of the hydrogen-containing silicone oil was tested using a Brookfield DV2TRV viscometer.

[0027] As a specific embodiment of the present invention, the hydrogen content in the hydrogen-containing silicone oil is 1.1wt% to 1.3wt%. For example, the hydrogen content in the hydrogen-containing silicone oil can be 1.1wt%, 1.15wt%, 1.2wt%, 1.25wt%, 1.3wt%, or a range thereof.

[0028] In a specific embodiment of the present invention, the modified silver powder is silver powder coated with silicone resin. The present invention does not have special requirements for the coating form, and it can be local adhesion, local coverage, local encapsulation, full encapsulation, etc.

[0029] As a specific embodiment of the present invention, the particle size D50 of the silver powder is 1 to 5 μm. For example, the particle size D50 of the silver powder can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or a range thereof.

[0030] The present invention found that when the particle size of silver powder is less than 1 μm, the viscosity of the prepared thermally conductive silicone rubber is too high and it is not suitable for practical applications. When the particle size of silver powder is greater than 5 μm, the thermal resistance of the prepared thermally conductive silicone rubber will be large, which is also not suitable for practical applications.

[0031] As a specific embodiment of the present invention, the softening point of the silicone resin is 60-70°C. For example, the softening point of the silicone resin can be 60°C, 62°C, 65°C, 68°C, 70°C or a range thereof.

[0032] This invention reveals that when the softening point of the silicone resin is 60–70°C, the viscosity and thermal conductivity of the prepared thermally conductive silicone rubber before curing meet the application requirements. It is believed that if the softening point of the silicone resin is below 60°C, during the curing process of the thermally conductive silicone rubber, the silicone resin softens before the hydrosilylation reaction between the vinyl-terminated polydimethylsiloxane, vinyl MQ resin, and hydrogen-containing silicone oil occurs. The softened silicone resin easily detaches from the silver powder surface, causing its encapsulation of the silver powder to fail, thus affecting the thermal conductivity of the prepared silicone rubber. If the softening point of the silicone resin is above 70°C, the hydrosilylation reaction has already been completed, and the silicone resin on the silver powder surface cannot form a miscibility with the system, resulting in reduced thermal conductivity.

[0033] In a specific embodiment of the present invention, the silicone resin can be methylphenyl silicone resin. In this invention, the silicone resin can be commercially available or manufactured in-house.

[0034] For example, the silicone resin is a reaction product of octamethylcyclotetrasiloxane, diphenyldimethoxysilane, and phenyltrimethoxysilane. The mass ratio of octamethylcyclotetrasiloxane, diphenyldimethoxysilane, and phenyltrimethoxysilane can be 120–140:420–460:800–1200.

[0035] In this invention, the method for preparing silicone resin includes:

[0036] (1) Mix and stir octamethylcyclotetrasiloxane, diphenyldimethoxysilane, phenyltrimethoxysilane, toluene, concentrated sulfuric acid and water to obtain a mixture;

[0037] (2) The mixture is allowed to stand and separated into an oil layer and a water layer. The water layer is removed, the pH value of the oil layer is adjusted, and the silicone resin is obtained by filtration, drying and crushing.

[0038] Preferably, the stirring in step (1) can be reflux stirring, and the preferred conditions for reflux stirring include: a temperature of 70-80°C and a time of 5-7 hours.

[0039] Preferably, in step (1), the amount of octamethylcyclotetrasiloxane is 120-140 parts by mass, the amount of diphenyldimethoxysilane is 420-460 parts, the amount of phenyltrimethoxysilane is 800-1200 parts, the amount of toluene is 600-1000 parts, the amount of concentrated sulfuric acid is 24-34 parts, and the amount of water is 420-600 parts.

[0040] Preferably, in step (2), the pH value of the oil layer is adjusted to 6.5 to 7.5.

[0041] Preferably, the water in step (1) is deionized water or distilled water.

[0042] Preferably, the concentration of concentrated sulfuric acid in step (1) is 97wt% to 99wt%, for example, the concentration of concentrated sulfuric acid is 97wt%, 98wt%, 99wt% or a range thereof.

[0043] As a specific embodiment of the present invention, the modified silver powder comprises 80 to 120 parts of silver powder and 4 to 6 parts of silicone resin by weight.

[0044] Preferably, the amount of silver powder in the modified silver powder can be 80 parts, 85 parts, 90 parts, 95 parts, 100 parts, 105 parts, 110 parts, 115 parts, 120 parts or a range thereof, based on parts by weight.

[0045] Preferably, the amount of silicone resin in the modified silver powder can be 4 parts, 4.5 parts, 5 parts, 5.5 parts, 6 parts, or a range thereof.

[0046] As a specific embodiment of the present invention, the method for preparing modified silver powder includes: mixing silicone resin, solvent and silver powder, drying and grinding to obtain modified silver powder.

[0047] Examples of solvents suitable for use in this invention include, but are not limited to, toluene. This invention does not have specific requirements regarding the amount of solvent, as long as it is sufficient to thoroughly mix the silicone rubber and silver powder. For example, the amount of solvent can be 180 to 220 parts by weight relative to 80 to 120 parts by weight of silver powder.

[0048] In a specific embodiment of the present invention, the grinding time during the preparation of modified silver powder is 8-10 hours. Specifically, the grinding is performed using a ball mill.

[0049] As a specific embodiment of the present invention, the thermally conductive silicone rubber comprises, by weight parts: 60-80 parts of vinyl-terminated polydimethylsiloxane, 20-40 parts of vinyl MQ resin, 3-5 parts of hydrogen-containing silicone oil, 0.008-0.012 parts of ethynylcyclohexanol, and 350-700 parts of modified silver powder.

[0050] The amount of vinyl polydimethylsiloxane in the thermally conductive silicone rubber can be 60 parts, 65 parts, 70 parts, 75 parts or 80 parts or a range thereof, based on parts by weight.

[0051] The amount of vinyl MQ resin in thermally conductive silicone rubber can be 20 parts, 25 parts, 30 parts, 35 parts, 40 parts or a range thereof, based on parts by weight.

[0052] The amount of hydrogen silicone oil in thermally conductive silicone rubber can be 3 parts, 3.5 parts, 4 parts, 4.5 parts, 5 parts, or a range thereof, based on parts by weight.

[0053] The amount of ethynylcyclohexanol in thermally conductive silicone rubber, by weight, can be 0.008 parts, 0.009 parts, 0.01 parts, 0.011 parts, 0.012 parts, or a range thereof.

[0054] The amount of modified silver powder in thermally conductive silicone rubber can be 350 parts, 400 parts, 450 parts, 500 parts, 550 parts, 600 parts, 650 parts, 700 parts or a range thereof, based on parts by weight.

[0055] Secondly, the present invention provides a method for preparing thermally conductive silicone rubber, comprising: mixing vinyl-terminated polydimethylsiloxane, vinyl MQ resin, hydrogen-containing silicone oil, ethynylcyclohexanol and modified silver powder in the presence of a catalyst to obtain thermally conductive silicone rubber.

[0056] In a specific embodiment of the present invention, the catalyst is a platinum complex.

[0057] Based on the amount of platinum used in the catalyst, the amount of catalyst used is 15 to 40 ppm of the total mass of the thermally conductive silicone rubber, excluding the modified silver powder.

[0058] Specifically, the platinum complex is a platinum complex of polyvinylsiloxane.

[0059] Specifically, the platinum complex catalyst is the Castells platinum catalyst.

[0060] As a specific embodiment of the present invention, the mixing time for preparing the thermally conductive silicone rubber is 0.2 to 0.5 h.

[0061] As a specific embodiment of the present invention, the mixing method for preparing thermally conductive silicone rubber is as follows: a mixture containing terminal vinyl polydimethylsiloxane, vinyl MQ resin, hydrogen-containing silicone oil, ethynylcyclohexanol and modified silver powder is mixed using a three-roll mill or a centrifuge to obtain a mixture, and the mixture is mixed in the three-roll mill or a centrifuge for 0.2 to 0.5 hours.

[0062] In this invention, the defined dosage, unless otherwise specified, generally refers to parts by weight.

[0063] Compared with the prior art, the present invention has the following beneficial effects.

[0064] The thermally conductive silicone rubber provided by this invention utilizes silver powder coated with silicone resin to achieve appropriate fluidity before curing (when the shear rate is 0.2 s⁻¹). -1 At the time of invention, the thermally conductive silicone rubber has a viscosity of 60,000–100,000 mPa·s and a high thermal conductivity. Therefore, the thermally conductive silicone rubber provided by this invention can meet the market demand for silicone rubber with ultra-high thermal conductivity.

[0065] The thermally conductive silicone rubber provided by this invention can be applied to heat dissipation components such as ultra-high power light-emitting chips. Detailed Implementation

[0066] The present invention will be further described below with reference to specific embodiments, but this does not constitute any limitation on the present invention.

[0067] All raw materials used in the embodiments of this invention are commercially available.

[0068] Among them, octamethylcyclotetrasiloxane was purchased from Hoshine Silicon Industry Co., Ltd.

[0069] Diphenyldimethoxysilane was purchased from Liaoning Xinbang New Materials Co., Ltd.

[0070] Phenylacetyltrimethoxysilane was purchased from Liaoning Xinbang New Materials Co., Ltd.

[0071] Toluene was purchased from Beijing Yili Fine Chemicals Co., Ltd.

[0072] Concentrated sulfuric acid, 98 wt%, purchased from Beijing Yili Fine Chemicals Co., Ltd.

[0073] Silver powder with a particle size D50 of 2μm was purchased from Jiangsu Boqian New Materials Co., Ltd.

[0074] Vinyl-terminated polydimethylsiloxane, with a dynamic viscosity of 10000 mPa·s at 25°C, was purchased from Shanghai Huazhirun Chemical Co., Ltd.

[0075] Vinyl MQ resin, with a molar ratio of M units to Q units of 1.05 and a vinyl content of 0.001 mol / g, was purchased from Chengdu Boda Aifu Technology Co., Ltd., model number 8201;

[0076] The hydrogen-containing silicone oil, with a dynamic viscosity of 25 mPa·s at 25°C, was purchased from Jiangxi Haiduo Organosilicon Materials Co., Ltd.

[0077] Ethynylcyclohexanol was purchased from Bailingwei Technology Co., Ltd. CAS.78-27-3;

[0078] The platinum complex catalyst was purchased from Shanghai Vivo Chemical Co., Ltd. (CAS. 68478-92-2). Before use, the platinum complex catalyst was diluted with vinyl-terminated polydimethylsiloxane to a platinum concentration of 1 wt%.

[0079] Synthesis of silicone resin

[0080] 130g of octamethylcyclotetrasiloxane, 440g of diphenyldimethoxysilane, 1000g of phenyltrimethoxysilane, 800g of toluene, 29g of concentrated sulfuric acid, and 510g of deionized water were mixed and refluxed at 70°C for 6 hours to obtain a mixture. The mixture was allowed to stand and cooled to room temperature, and an oil layer and an aqueous layer were separated. The aqueous layer was removed. Sodium bicarbonate was added to the oil layer to adjust the pH to 7, and the mixture was stirred at room temperature for 1 hour. After filtration, the mixture was dried and crushed to form a silicone resin.

[0081] The test method for the softening point of silicone resin is as follows:

[0082] Instrument: PerkinElmer Differential Scanning Calorimeter, Model: DSC6000;

[0083] Test method: Heating from -85℃ to 150℃ at a rate of 10℃ / min;

[0084] The TG point was measured using DSC: the softening point of the silicone resin was 65.2℃.

[0085] Synthesis of modified silver powder

[0086] Weigh 50g of the prepared silicone resin and mix it with 2000g of toluene. Stir to dissolve the mixture, then add 1000g of silver powder with a D50 value of 2μm. Stir at room temperature for 8 hours to obtain a mixture. Dry the mixture and grind it in a ball mill for 8 hours to obtain modified silver powder.

[0087] In a specific embodiment of the present invention, the above-described synthesis steps of silicone resin and modified silver powder are repeated to obtain sufficient amounts of silicone resin and modified silver powder for use in the examples and comparative examples.

[0088] Example 1

[0089] Weigh 70g of vinyl polydimethylsiloxane, 30g of vinyl MQ resin, 4.3g of hydrogen-containing silicone oil with a hydrogen content of 1.2wt%, 0.01g of ethynylcyclohexanol, 0.3g of diluted platinum complex catalyst, and 350g of modified silver powder. Mix them in a three-roll mill for 0.5h to obtain thermally conductive silicone rubber.

[0090] Example 2

[0091] Weigh 60g of vinyl polydimethylsiloxane, 40g of vinyl MQ resin, 4.8g of hydrogen-containing silicone oil with a hydrogen content of 1.1wt%, 0.01g of ethynylcyclohexanol, 0.3g of diluted platinum complex catalyst, and 400g of modified silver powder. Mix them in a three-roll mill for 0.5h to obtain thermally conductive silicone rubber.

[0092] Example 3

[0093] Weigh 80g of vinyl polydimethylsiloxane, 20g of vinyl MQ resin, 3.9g of hydrogen-containing silicone oil with a hydrogen content of 1.3wt%, 0.01g of ethynylcyclohexanol, 0.3g of diluted platinum complex catalyst, and 650g of modified silver powder. Mix them in a three-roll mill for 0.5h to obtain thermally conductive silicone rubber.

[0094] Example 4

[0095] Weigh 60g of vinyl polydimethylsiloxane, 40g of vinyl MQ resin, 4.5g of hydrogen-containing silicone oil with a hydrogen content of 1.2wt%, 0.01g of ethynylcyclohexanol, 0.3g of diluted platinum complex catalyst, and 700g of modified silver powder. Mix them in a three-roll mill for 0.5h to obtain thermally conductive silicone rubber.

[0096] Comparative Example 1

[0097] Comparative Example 1 was set up based on Example 1. The difference between Comparative Example 1 and Example 1 is that the thermally conductive silicone rubber was prepared by directly using silver powder with a d50 value of 2μm. That is, no modification treatment was performed on the silver powder.

[0098] Comparative Example 2

[0099] Comparative Example 2 was set up based on Example 1. The difference between Comparative Example 2 and Example 1 is that the synthesis process of the modified silver powder is as follows:

[0100] 50g of silicone resin and 2000g of toluene were dissolved by stirring, and then 1000g of silver powder with a D50 value of 2μm was added. The mixture was stirred at room temperature for 8 hours, dried, and then ground to obtain modified silver powder. The silicone resin used had a softening point of 51.6℃.

[0101] The synthesis method of silicone resin with a softening point of 51.6℃ is as follows: 130g of octamethylcyclotetrasiloxane, 440g of diphenyldimethoxysilane, 500g of phenyltrimethoxysilane, 800g of toluene, 29g of concentrated sulfuric acid, and 510g of deionized water are mixed and stirred under reflux at 70℃ for 6 hours to obtain a mixture. The mixture is allowed to stand and cooled to room temperature, and the mixture separates into an oil layer and an aqueous layer. The aqueous layer is separated. Sodium bicarbonate is added to the oil layer to adjust the pH to 7, and the mixture is stirred at room temperature for 1 hour. After filtration, a mixture is obtained, which is then dried and crushed to form silicone resin. The softening point of the silicone resin is tested to be 51.6℃.

[0102] Comparative Example 3

[0103] Comparative Example 3 was set up based on Example 1. The difference between Comparative Example 3 and Example 1 is that the synthesis process of the modified silver powder is as follows:

[0104] 50g of silicone resin and 2000g of toluene were dissolved by stirring, and then 1000g of silver powder with a d50 value of 2μm was added. The mixture was stirred at room temperature for 8 hours, dried, and then ground to obtain modified silver powder. The silicone resin used had a softening point of 78.9℃.

[0105] The synthesis method of silicone resin with a softening point of 78.9℃ is as follows: 130g of octamethylcyclotetrasiloxane, 440g of diphenyldimethoxysilane, 1500g of phenyltrimethoxysilane, 800g of toluene, 29g of concentrated sulfuric acid, and 510g of deionized water are mixed and refluxed at 70℃ for 6 hours to obtain a mixture. The mixture is allowed to stand and cooled to room temperature, and the mixture separates into an oil layer and an aqueous layer. The aqueous layer is separated. Sodium bicarbonate is added to the oil layer to adjust the pH to 7, and the mixture is stirred at room temperature for 1 hour. After filtration, the mixture is dried and crushed to form silicone resin. The softening point of the silicone resin is tested to be 78.9℃.

[0106] Comparative Example 4

[0107] Comparative Example 4 was set up based on Example 1. The difference between Comparative Example 4 and Example 1 is that the preparation process of the modified silver powder is as follows:

[0108] Weigh 50g of the silicone resin with a softening point of 65.2℃ and 2000g of toluene, stir to dissolve, and add 1000g of silver powder with a d50 value of 8μm. Stir at room temperature for 8 hours, dry, and grind to obtain modified silver powder.

[0109] Comparative Example 5

[0110] Comparative Example 5 was set up based on Example 1. The difference between Comparative Example 5 and Example 1 is that the preparation process of the modified silver powder is as follows:

[0111] Weigh 30g of the silicone resin with a softening point of 65.2℃ and 2000g of toluene prepared above, stir to dissolve, and add 1200g of silver powder with a d50 value of 2μm. Stir at room temperature for 8 hours, dry, and grind to obtain modified silver powder.

[0112] Comparative Example 6

[0113] Comparative Example 6 was set up based on Example 1. The difference between Comparative Example 6 and Example 1 is that the preparation process of the modified silver powder is as follows:

[0114] Weigh 70g of the silicone resin with a softening point of 65.2℃ and 2000g of toluene prepared above, stir to dissolve, and add 800g of silver powder with a d50 value of 2μm. Stir at room temperature for 8 hours, dry, and grind to obtain modified silver powder.

[0115] The thermally conductive silicone rubbers prepared in Examples 1-4 and Comparative Examples 1-6 were subjected to performance tests.

[0116] Viscosity test of thermally conductive silicone rubber

[0117] Instrument: Anton Paar rheometer

[0118] Model: MCR102

[0119] Test conditions: 0.2S -1 10min

[0120] Thermal conductivity test of thermally conductive silicone rubber

[0121] Instrument: Hot Disk thermal constant analyzer

[0122] Test principle: Transient planar heat source method

[0123] Sample preparation requirements: 30*30*0.2mm test sample, cured at 150℃ for 2 hours.

[0124] Hardness test of thermally conductive silicone rubber after thermosetting

[0125] Instrument: Shore A hardness tester

[0126] Sample preparation requirements: 20*10*20mm square block, cured at 150℃ for 2 hours.

[0127] Table 1. Test results of the thermally conductive silicone rubbers prepared in Examples 1-4 and Comparative Examples 1-6

[0128] As can be seen from the comparison of the examples and comparative examples, the thermally conductive silicone rubber prepared by the present invention has a suitable viscosity, which ensures that the flowability of the thermally conductive silicone rubber before curing meets the application requirements, and also has a relatively high thermal conductivity. The thermally conductive silicone rubber prepared by the present invention has a wide range of applications.

[0129] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A thermally conductive silicone rubber, characterized in that, The thermally conductive silicone rubber comprises: vinyl-terminated polydimethylsiloxane, vinyl MQ resin, hydrogen-containing silicone oil, ethynylcyclohexanol, and modified silver powder; the modified silver powder is a mixture containing silicone resin and silver powder.

2. The thermally conductive silicone rubber according to claim 1, characterized in that, The thermal conductivity of the thermally conductive silicone rubber is 10–18 W / (m·K); the hardness of the cured thermally conductive silicone rubber is 50–95 A; and the shear rate is 0.2 s⁻¹ at a temperature of 25°C. -1 At that time, the viscosity of the thermally conductive silicone rubber was 60,000 to 100,000 mPa·s.

3. The thermally conductive silicone rubber according to claim 1 or 2, characterized in that, At 25°C, the dynamic viscosity of the vinyl-terminated polydimethylsiloxane is 200–500,000 mPa·s, preferably 3,000–20,000 mPa·s; And / or, the vinyl content of the vinyl MQ silicone resin is 0.0006 to 0.002 mol / g; And / or, the molar ratio of M units to Q units in the vinyl MQ silicone resin is 0.9 to 1.

1.

4. The thermally conductive silicone rubber according to claim 1 or 2, characterized in that, The silicone rubber comprises, by weight parts: 60-80 parts of vinyl-terminated polydimethylsiloxane, 20-40 parts of vinyl MQ resin, 3-5 parts of hydrogen-containing silicone oil, 0.008-0.012 parts of ethynylcyclohexanol, and 350-700 parts of modified silver powder.

5. The thermally conductive silicone rubber according to any one of claims 1 to 3, characterized in that, The hydrogen content in the hydrogen-containing silicone oil is 1.1% to 1.3% by mass; And / or, at a temperature of 25°C, the dynamic viscosity of the hydrogen-containing silicone oil is 10–200 mPa·s, preferably 15–50 mPa·s.

6. The thermally conductive silicone rubber according to any one of claims 1 to 5, characterized in that, The modified silver powder comprises, by weight, 4-6 parts of silicone resin and 80-120 parts of silver powder.

7. The thermally conductive silicone rubber according to claim 6, characterized in that, The method for preparing the modified silver powder includes: mixing silicone resin, solvent and silver powder, drying and grinding to obtain modified silver powder; Preferably, the solvent is toluene; Preferably, the d50 value of the silver powder is 1-5 μm; Preferably, the grinding time is 8 to 10 hours.

8. The thermally conductive silicone rubber according to any one of claims 1 to 7, characterized in that, The softening point of the silicone resin is 60-70°C; And / or, the silicone resin is a reaction product of octamethylcyclotetrasiloxane, diphenyldimethoxysilane, and phenyltrimethoxysilane; Preferably, the mass ratio of octamethylcyclotetrasiloxane, diphenyldimethoxysilane, and phenyltrimethoxysilane can be 120–140:420–460:800–1200.

9. The thermally conductive silicone rubber according to claim 8, characterized in that, The method for preparing the silicone resin includes: (1) Mix and stir octamethylcyclotetrasiloxane, diphenyldimethoxysilane, phenyltrimethoxysilane, toluene, concentrated sulfuric acid and water to obtain a mixture; (2) The mixture is allowed to stand and separated into an oil layer and a water layer. The water layer is removed, the pH value of the oil layer is adjusted, and the silicone resin is obtained by filtration, drying and crushing. Preferably, the water is deionized water or distilled water; Preferably, the concentration of the concentrated sulfuric acid is 97 wt% to 99 wt%. Preferably, the stirring is reflux stirring, and the conditions for reflux stirring include: a temperature of 70-80°C and a time of 5-7 hours; And / or, adjust the pH of the oil layer to 6.5–7.

5.

10. A method for preparing the thermally conductive silicone rubber according to any one of claims 1 to 9, characterized in that, The preparation method includes: mixing terminal vinyl polydimethylsiloxane, vinyl MQ resin, hydrogen-containing silicone oil, ethynylcyclohexanol and modified silver powder in the presence of a catalyst to obtain the thermally conductive silicone rubber.

11. The method for preparing thermally conductive silicone rubber according to claim 10, characterized in that, The catalyst is a platinum complex, and the amount of the catalyst is such that the mass of the platinum is 15 to 40 ppm of the total mass of the thermally conductive silicone rubber, excluding the modified silver powder. And / or, the mixing time is 0.2 to 0.5 h.

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