A method for producing low-oil-penetration, low-volatility, non-curing thermally conductive silicone gel

Abstract

The invention relates to the technical field of thermal conductive materials, and in particular to a method for producing a low-oil permeability, low-volatility, non-solidifying thermal conductive silicone gel; the method comprises the following steps: S1: preparing a special silicone oil containing a coupling agent hydrophilic group, an alkoxy group; S2: preparing a dimethyl silicone oil with a comb structure; S3: uniformly mixing the special silicone oil in S1 and the dimethyl silicone oil in S2 with thermal conductive powder in a certain proportion under vacuum conditions, and obtaining the low-oil permeability, low-volatility, non-solidifying thermal conductive silicone gel after standing and hydrolyzing completely. The invention utilizes the principle of molecular design to, on the one hand, introduce the hydrophilic group of the coupling agent into the silicone oil molecule to obtain the special silicone oil that can form a chemical connection with the powder surface; on the other hand, preparing the dimethyl silicone oil with a comb structure, uniformly mixing the above two silicone oils with a thermal conductive filler in a certain proportion, and obtaining the non-solidifying thermal conductive silicone gel with the characteristics of low volatility and low oil permeability after complete hydrolysis.

Description

Technical Field

[0001] The invention relates to the technical field of thermal conductive materials, and in particular to a production method of low-oil-permeability, low-volatility, non-solidifying thermal conductive silicone gel. Background Art

[0002] Thermally conductive silicone gel, invented by Parker Chomerics in the early 2000s, is a colloid that lies somewhere between a thermally conductive silicone pad and a thermally conductive paste. It is a composition prepared by mixing and dispersing linear silicone oil and thermally conductive fillers through a process known as mixing and dispersion. Currently, the thermal conductivity of commercially available thermally conductive gels is generally below 3W / (m·K), which is insufficient to meet the current market's high thermal conductivity requirements. Furthermore, these thermally conductive gels are limited by their formulation and process, resulting in high viscosity and oil permeability, making it difficult to maintain stable performance.

[0003] Thermal conductive silicone gels are classified into two types according to whether they can undergo cross-linking reactions: curable and non-curable. Relatively speaking, curable gels can more easily meet customers' technical requirements for low oil permeability and low volatility due to cross-linking reactions, while non-curable silicone gels have the risk of oil permeation, volatility, and even sagging, which greatly limits the application of this type of material in related industries. Summary of the Invention

[0004] In order to solve the above problems, the purpose of the present invention is to provide a method for producing low oil permeability, low volatility, non-solidifying thermally conductive silicone gel. To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0005] A method for producing low-oil-penetration, low-volatility, non-curing thermally conductive silicone gel comprises the following steps:

[0006] S1: Preparation of special silicone oil containing coupling agent hydrophilic group - alkoxy;

[0007] S2: Preparation of dimethyl silicone oil with comb structure;

[0008] S3: The special silicone oil in S1 and the dimethyl silicone oil in S2 are mixed evenly with the thermal conductive powder in a certain proportion under vacuum conditions, and after standing and hydrolyzing completely, a low-oil-permeability, low-volatile, non-curing thermal conductive silicone gel is obtained.

[0009] In the S1, a coupling agent containing a hydrophilic group and hydrogen-containing silicone oil are reacted in the presence of a platinum catalyst to prepare a special silicone oil containing an alkoxy group.

[0010] The coupling agent is selected from one of vinyltrimethoxysilane, vinyltriethoxysilane and vinyltriisopropoxysilane.

[0011] In the step S2, single-end vinyl silicone oil and hydrogen-containing silicone oil are reacted with a platinum catalyst to obtain a reactant, and the reactant is then subjected to column chromatography to obtain purified dimethyl silicone oil with a comb-like structure.

[0012] The viscosity of the hydrogenated silicone oil used in S1 and S2 is 500 cps.

[0013] The temperature of the reaction system in S1 and S2 is 100°C.

[0014] The viscosity of the single-end vinyl silicone oil in S2 is 100-300 cps.

[0015] Although the platinum content in the platinum catalyst used in S1 and S2 is 25000 ppm.

[0016] In S3, the special silicone oil prepared in S1 and the dimethyl silicone oil prepared in S2 are stirred evenly with isopropyl titanate triisostearate and spherical alumina under vacuum to obtain a thermally conductive silicone gel.

[0017] The spherical aluminum oxide has a diameter selected from a combination of 2 μm and 20 μm.

[0018] Before gelling, the resin's fluidity allows for pouring, infiltration, and other processes, making gel time a crucial process parameter. Curing at low temperature first, then at high temperature, or directly curing at high temperature can produce different properties. Direct high temperature curing results in a rapid release of reaction heat, raising the temperature inside the casting, altering the reaction mechanism, and even causing epoxy resin degradation or aging, ultimately resulting in a potential decline in performance. Curing at low temperature first, followed by post-curing when the degree of cure reaches a certain level, slows the reaction rate and reduces the accumulation of reaction heat. This allows for a higher degree of cure without thermal aging or degradation, resulting in material properties that are significantly better than curing directly at high temperature.

[0019] The present invention has the following beneficial effects: Utilizing molecular design principles, the present invention introduces hydrophilic groups (e.g., hydrolysis-reactive alkoxy groups such as trimethoxy, triethoxy, or tripropoxy) from a coupling agent into silicone oil molecules, yielding a specialized silicone oil capable of forming a chemical bond with the powder surface. Furthermore, the invention prepares a dimethyl silicone oil with a comb-like structure. Compared to conventional linear silicone oils, comb-like silicone oils offer greater resistance to chain segment motion in the thermally conductive gel, resulting in greater room-temperature storage stability without significantly increasing the gel's hardness, as occurs with cross-linked silicone oil systems. By uniformly mixing these two silicone oils with a thermally conductive filler in a specific ratio and allowing complete hydrolysis, a non-curing thermally conductive silicone gel with low volatility and low oil permeability can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1Volatility test charts of gel 1, gel 2, and gel 3 prepared in Examples 1-3 of the present invention, as well as a comparative gel;

[0021] Figure 2 Oil permeation test charts of gel 1, gel 2, and gel 3 prepared in Examples 1-3 of the present invention, as well as a comparative gel. DETAILED DESCRIPTION

[0022] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but the present invention is not limited to the scope of the embodiments.

[0023] The process parameters not specified in the examples of this application can be carried out according to conventional methods, and the raw materials used can be obtained through commercial channels.

[0024] Example 1

[0025] In a three-necked flask drying system equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 4.73 g of vinyltrimethoxysilane and 100 g of hydrogen-containing silicone oil with a viscosity of 500 cps and a hydrogen content of 0.32 mmol / g were added in sequence under nitrogen protection. 0.05 g of a platinum catalyst with a platinum content of 25,000 ppm was added under mechanical stirring. The temperature was raised to 100°C and stirred at this constant temperature for 2 hours. Then, small molecules were removed by distillation under reduced pressure to obtain a special silicone oil with a trimethoxy group, which was recorded as Silicone Oil 1.

[0026] In a three-necked flask drying system equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 62 g of single-ended vinyl silicone oil with a viscosity of 100 cps and 100 g of hydrogen-containing silicone oil with a viscosity of 500 cps and a content of 0.32 mmol / g were added in sequence under nitrogen protection. 0.05 g of a platinum catalyst with a platinum content of 25,000 ppm was added under mechanical stirring. The temperature was slowly raised to 100°C and stirred at this constant temperature for 2 h. Small molecules were then removed by distillation under reduced pressure, and purified comb-shaped specialty silicone oil with a viscosity of approximately 1,000 cps was obtained by column chromatography, which was recorded as Silicone Oil 2.

[0027] 200 g of silicone oil 1, 1200 g of silicone oil 2, 50 g of isopropyl titanate triisostearate, 2565 g of spherical alumina with a D50 of 2 μm, and 5985 g of spherical alumina with a D50 of 20 μm were added to a double planetary vacuum mixer. After vacuum stirring for 2 hours, the mixture was allowed to stand at room temperature for 48 hours to obtain a thermal conductive silicone gel, which was recorded as gel 1.

[0028] Example 2

[0029] In a three-necked flask drying system equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 5.91 g of vinyltriethoxysilane and 100 g of hydrogen-containing silicone oil with a viscosity of 500 cps and a hydrogen content of 0.4 mmol / g were added in sequence under nitrogen protection. 0.05 g of a platinum catalyst with a platinum content of 25,000 ppm was added under mechanical stirring. The temperature was raised to 100°C and stirred at this constant temperature for 2 h. Then, small molecules were removed by vacuum distillation to obtain a special silicone oil with a trimethoxy group, which was recorded as Silicone Oil 3.

[0030] In a three-necked flask drying system equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 30 g of single-ended vinyl silicone oil with a viscosity of 300 cps and 100 g of hydrogen-containing silicone oil with a viscosity of 500 cps and a content of 0.32 mmol / g were added in sequence under nitrogen protection. 0.05 g of a platinum catalyst with a platinum content of 25,000 ppm was added under mechanical stirring. The temperature was slowly raised to 100°C and stirred at this temperature for 10 hours. Small molecules were then removed by distillation under reduced pressure, and purified comb-shaped specialty silicone oil with a viscosity of approximately 1,000 cps was obtained by column chromatography, which was recorded as Silicone Oil 4.

[0031] 200 g of silicone oil 3, 1200 g of silicone oil 4, 50 g of isopropyl titanate triisostearate, 2565 g of spherical alumina with a D50 of 2 μm, and 5985 g of spherical alumina with a D50 of 20 μm were added to a double planetary vacuum mixer. After vacuum stirring for 2 hours, the mixture was allowed to stand at room temperature for 48 hours to obtain a thermal conductive silicone gel, which was recorded as gel 2.

[0032] Example 3

[0033] In a three-necked flask drying system equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 3.7 g of vinyltriisopropoxysilane and 100 g of hydrogen-containing silicone oil with a viscosity of 500 cps and a hydrogen content of 0.25 mmol / g were added in sequence under nitrogen protection. 0.05 g of a platinum catalyst with a platinum content of 25,000 ppm was added under mechanical stirring. The temperature was raised to 100°C and stirred at this constant temperature for 2 hours. Then, small molecules were removed by vacuum distillation to obtain a special silicone oil with a trimethoxy group, which was recorded as Silicone Oil 5.

[0034] In a three-necked flask drying system equipped with a stirrer, a nitrogen inlet tube, and a reflux condenser, 47 g of single-ended vinyl silicone oil with a viscosity of 200 cps and 100 g of hydrogen-containing silicone oil with a viscosity of 500 cps and a content of 0.32 mmol / g were added in sequence under nitrogen protection. Under mechanical stirring conditions, 0.05 g of a platinum catalyst with a platinum content of 25,000 ppm was added. The temperature was slowly raised to 100°C and stirred at this constant temperature for 10 hours. Then, small molecules were removed by distillation under reduced pressure, and purified comb-shaped specialty silicone oil with a viscosity of approximately 1,000 cps was obtained by column chromatography, which was recorded as Silicone Oil 6.

[0035] 200 g of silicone oil 5, 1200 g of silicone oil 6, 50 g of isopropyl titanate triisostearate, 2565 g of spherical alumina with a D50 of 2 μm, and 5985 g of spherical alumina with a D50 of 20 μm were added to a double planetary vacuum mixer. After vacuum stirring for 2 hours, the mixture was allowed to stand at room temperature for 96 hours to obtain a thermal conductive silicone gel, which was recorded as gel 3.

[0036] Comparative experiment

[0037] 1400g of dimethyl silicone oil with a viscosity of 2000cps, 50g of isopropyl titanate triisostearate, 2565g of spherical alumina with a D50 of 2um, and 5985g of spherical alumina with a D50 of 20um were added to a double planetary vacuum mixer. After vacuum stirring for 2 hours, the mixture was allowed to stand for 48 hours to obtain a comparative thermal conductive silicone gel, which was recorded as comparative gel.

[0038] Volatility comparison: Put 10g of each of the above four gels into four 250ml conical flasks, cover the flask mouth with a transparent glass sheet, put the conical flask on a 150℃ heating table, and observe the oil stains on the glass sheet after 48 hours. Figure 1 Compared with the control gel, gel 1, gel 2 and gel 3 prepared in Examples 1-3 did not volatilize and adhere to the glass sheet during the test;

[0039] Comparison of oil seepage results: Gel 1, Gel 2, Gel 3 and the control gel were made into 80mm long, 5mm wide and 2mm high strips on grid paper using a dispensing machine. Then they were placed in a 55℃ oven for 14 days and the size of the oil seepage area was observed. Figure 2 Gel 1, Gel 2 and Gel 3 prepared in Examples 1-3 of the present invention did not ooze oil on the grid paper, while the comparison gel commonly used in the prior art did ooze oil significantly.

[0040] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for producing low oil permeability, low volatility, non-curing thermally conductive silicone gel, characterized in that: The following steps are involved: S1: Preparation of special silicone oil containing coupling agent hydrophilic group - alkoxy; S2: Preparation of dimethyl silicone oil with comb-like structure; S3: The special silicone oil in S1 and the dimethyl silicone oil in S2 are mixed with the thermal conductive powder in a certain proportion under vacuum conditions, and the mixture is allowed to stand and hydrolyze completely to obtain a low-oil-permeability, low-volatile, non-solidifying thermal conductive silicone gel; In said S1, a coupling agent containing a hydrophilic group and hydrogen-containing silicone oil are reacted with a platinum catalyst to prepare a special silicone oil containing an alkoxy group; The coupling agent is selected from one of vinyltrimethoxysilane, vinyltriethoxysilane and vinyltriisopropoxysilane; In S2, single-end vinyl silicone oil and hydrogen-containing silicone oil are reacted under the action of a platinum catalyst to obtain a reactant, and the reactant is then subjected to column chromatography to obtain purified comb-shaped dimethyl silicone oil; The viscosity of the hydrogenated silicone oil used in S1 and S2 is 500 cps.

2. The method for producing a low oil permeability, low volatility, non-curing thermally conductive silicone gel according to claim 1, characterized in that: The temperature of the reaction system in S1 and S2 is 100°C.

3. The method for producing a low oil permeability, low volatility, non-curing thermally conductive silicone gel according to claim 1, characterized in that: The viscosity of the single-end vinyl silicone oil in S2 is 100-300 cps.

4. The method for producing a low oil permeability, low volatility, non-curing thermally conductive silicone gel according to claim 1, characterized in that: The platinum content in the platinum catalyst used in S1 and S2 is 25000 ppm.

5. The method for producing a low oil permeability, low volatility, non-curing thermally conductive silicone gel according to claim 1, characterized in that: In S3, the special silicone oil prepared in S1 and the dimethyl silicone oil prepared in S2 are stirred evenly with isopropyl titanate triisostearate and spherical alumina under vacuum to obtain a thermally conductive silicone gel.

6. The method for producing a low oil permeability, low volatility, non-curing thermally conductive silicone gel according to claim 5, characterized in that: The spherical aluminum oxide has a diameter selected from a combination of 2 μm and 20 μm.

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