Low-density adhesive organic silicon pouring sealant and preparation method thereof

Abstract

The invention relates to the technical field of organic silicon pouring sealants, in particular to a low-density adhesion organic silicon pouring sealant and a preparation method thereof.The low-density adhesion organic silicon pouring sealant comprises a component A and a component B. The component A comprises, by mass, 40-60 parts of vinyl polydimethylsiloxane A; 0.1 to 1 part of a platinum catalyst; 40 to 65 parts of filler A; the component B is prepared from the following raw materials in parts by mass: 20 to 40 parts of vinyl polydimethylsiloxane B; 10 to 25 parts of hydrogen-containing silicone oil; 40 to 65 parts of filler B; 0.05 to 0.2 part of an inhibitor; and 1 to 2.5 parts of a tackifier. The product has the advantages of low density, low viscosity, good fluidity and excellent adhesion, does not influence the platinum catalytic curing efficiency, and better meets the actual application requirements.

Description

Technical Field

[0001] This invention relates to the field of silicone potting compound technology, specifically to a low-density adhesive silicone potting compound and its preparation method. Background Technology

[0002] Addition-type silicone potting compounds are widely used for component encapsulation and protection in electronics, new energy vehicles, and solar photovoltaic industries due to their excellent high and low temperature resistance, electrical insulation, weather resistance, and environmental friendliness. As electronic devices become smaller and lighter, lower density requirements are being placed on potting compounds to reduce overall weight. Simultaneously, the potting compound needs to have good adhesion to substrates such as metal casings (e.g., aluminum alloys) and printed circuit boards (PCBs) to prevent moisture and dust intrusion and interface delamination caused by thermal expansion and contraction, ensuring long-term reliability.

[0003] Traditional addition-cure silicone potting compounds have high density and limited adhesion to non-polar substrates. To improve adhesion, tackifiers, such as silane coupling agents containing epoxy, amino, or isocyanate groups, are often added. For example, Chinese patent application (publication number CN117777458A) discloses a low-density silicone potting compound and its preparation method that prevents bubbling. This method modifies the surface of hollow glass microspheres with amphiphilic fluorinated polysiloxanes, thereby improving the compatibility with silicone oil and reducing density. However, these highly reactive groups can easily poison the platinum catalyst in addition-cure silicone rubber, preventing the compound from curing or causing incomplete curing. If physical blending fillers are used to achieve flame retardancy and reduce density, it often leads to a sharp increase in viscosity, decreased thixotropy, and poor flowability, making it difficult to pot complex and small gaps. For example, the international patent application (publication number WO2024108681A1) discloses an ultra-low density ultra-flame-retardant silicone thermal insulation potting compound and its preparation method. By modifying the surface of lightweight fillers, using an outer coating of porous carbon layer and calcium fluoride, and adding silicon, phosphorus and vinyl to the polymer chain segments, the compatibility and flame retardant properties of the fillers are improved to a certain extent. However, it still cannot effectively overcome the above problems. Summary of the Invention

[0004] To address the aforementioned issues, this invention provides a low-density adhesive silicone potting compound that combines low density, low viscosity, good flowability, and excellent adhesion without affecting the platinum catalytic curing efficiency, thus better meeting practical application needs.

[0005] This invention provides a low-density adhesive silicone potting compound, comprising component A and component B, wherein component A, by weight, comprises the following raw materials: Vinyl polydimethylsiloxane A: 40-60 parts, wherein the viscosity of vinyl polydimethylsiloxane A at 25°C is 100-500 mPa·s; Platinum catalyst: 0.1-1 part; Packing material A: 40-65 parts; Component B, by mass, comprises the following raw materials: Vinyl polydimethylsiloxane B: 20-40 parts, wherein the viscosity of vinyl polydimethylsiloxane B at 25°C is 100-500 mPa·s; Hydrogen-containing silicone oil: 10-25 parts; Packing material B: 40-65 parts; Inhibitor: 0.05-0.2 parts; Tackifier: 1-2.5 parts; the tackifier is prepared by hydrolysis and condensation reaction of the following raw materials in parts by weight: 25-35 parts of tetraethyl orthosilicate, 25-50 parts of octamethylcyclotetrasiloxane, 10-30 parts of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 5-20 parts of phenyl / methyl / vinyltrimethoxysilane, 3-15 parts of γ-methacryloyloxypropyltrimethoxysilane, and 15-20 parts of catalyst solution.

[0006] Existing silicone potting compounds cannot effectively balance adhesion, flowability, and curing performance. During the research process, this invention discovered that by using specific raw materials to prepare a tackifier through hydrolysis and condensation, and further controlling the amount of tackifier added, combined with viscosity control of vinyl polydimethylsiloxanes A and B, the product can simultaneously possess excellent adhesion and flowability without affecting curing performance. It can fill various irregular gaps, exhibits good adhesion to metal casings, PCBs, etc., and is suitable for potting various electronic component circuit board supports, PCBs, and the new energy industry. It does not delaminate or crack from the circuit board substrate and has waterproof and corrosion-resistant effects. The inventors analyzed that the reason might be as follows: using tetraethyl orthosilicate, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, phenyl / methyl / vinyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane as the backbone, hydrolysis is carried out under an acidic catalyst to generate silanol groups (Si-OH), which are further condensed to form a tackifier containing active Si-OH terminals, phenyl groups, and γ-methacryloyloxypropyl groups. This tackifier has moderate activity and will not poison the platinum catalyst, ensuring the normal progress of the addition-curing reaction. At the same time, high-strength adhesion to the substrate surface can be achieved through the combined effects of chemical anchoring (covalent bonds), physical anchoring, and interface reinforcement. Based on this, by controlling the viscosity of the vinyl polydimethylsiloxanes A and B at 25°C to be 100-500 mPa·s, and with the addition of an appropriate amount of tackifier, the mixed viscosity is maintained at 2000. With a thixotropic index between 1.6 and 2.0 and a pressure below mPa·s, it exhibits good fluidity and moderate thixotropy, facilitating potting construction without sagging.

[0007] In one embodiment, the vinyl polydimethylsiloxane A includes vinyl polydimethylsiloxane A1 with a viscosity of 300-400 mPa·s at 25°C and vinyl polydimethylsiloxane A2 with a viscosity of 100-200 mPa·s at 25°C.

[0008] In one embodiment, the mass ratio of vinyl polydimethylsiloxane A1 to vinyl polydimethylsiloxane A2 is 2-3.5:1.5-3.

[0009] In one embodiment, the mass ratio of vinyl polydimethylsiloxane A1 to vinyl polydimethylsiloxane A2 is 25-28:20.5-25.

[0010] In one embodiment, the filler A comprises aluminum hydroxide A and hollow glass microspheres A.

[0011] In one embodiment, the mass ratio of aluminum hydroxide A to hollow glass microspheres A is 35-55:2-5.

[0012] In one embodiment, the mass ratio of aluminum hydroxide A to hollow glass microspheres A is 45-48:3-4.

[0013] In one embodiment, the particle size D50 of the aluminum hydroxide A is 1-40 μm.

[0014] In one embodiment, the particle size D50 of the aluminum hydroxide A is 10-20 μm.

[0015] In one embodiment, the aluminum hydroxide A has a particle size D50 of 12-15 μm, is model FR-3815, and is sourced from Hefei Zhongke Flame Retardant New Materials Co., Ltd.

[0016] In one embodiment, the hollow glass microspheres A have a particle size D50 of 10-80 μm and a density of 0.1-0.4 g / cm³. 3 .

[0017] In one embodiment, the hollow glass microspheres A have a particle size D50 of 40-50 μm and a density of 0.12-0.15 g / cm³. 3 .

[0018] In one embodiment, the hollow glass microspheres A have a particle size D50 of 40 μm and a density of 0.15 g / cm³. 3 Model number K15HSN, sourced from 3M. TM Hollow glass microspheres.

[0019] This invention utilizes a compound of high-filling-content aluminum hydroxide (particle size 1-40 μm) and low-density hollow glass microspheres (particle size 10-80 μm, density 0.1-0.4 g / cm³). 3 While ensuring flame retardancy, the density of the cured adhesive was effectively reduced to 1.0 g / cm³. 3 At the same time, the thixotropic properties of the product are adjusted to better meet the needs of actual applications.

[0020] In one embodiment, the vinyl polydimethylsiloxane B includes vinyl polydimethylsiloxane B1 with a viscosity of 300-400 mPa·s at 25°C and vinyl polydimethylsiloxane B2 with a viscosity of 100-200 mPa·s at 25°C.

[0021] In one embodiment, the mass ratio of vinyl polydimethylsiloxane B1 to vinyl polydimethylsiloxane B2 is 20-30:3-10.

[0022] The mass ratio of vinyl polydimethylsiloxane B1 to vinyl polydimethylsiloxane B2 is 20-25:5.65-8.

[0023] In one embodiment, the hydrogen-containing silicone oil includes terminal hydrogen-containing silicone oil and side-chain hydrogen-containing silicone oil.

[0024] In one embodiment, the mass ratio of the end-chain hydrogen-containing silicone oil to the side-chain hydrogen-containing silicone oil is 8-15:3-8.

[0025] In one embodiment, the mass ratio of the end-chain hydrogen-containing silicone oil to the side-chain hydrogen-containing silicone oil is 10-13:4-6.

[0026] In one embodiment, the hydrogen content of the end-hydrogen-containing silicone oil is 0.05-0.5 wt%, and the hydrogen content of the side-chain hydrogen-containing silicone oil is 0.8-1.0 wt%.

[0027] In one embodiment, the end-chain hydrogen-containing silicone oil is model HD-202L, sourced from Jiangxi Haiduo Organosilicon Materials Co., Ltd.; the side-chain hydrogen-containing silicone oil is model H-202L, sourced from Jiangxi Haiduo Organosilicon Materials Co., Ltd.

[0028] This invention uses a compound of end-chain hydrogen-containing silicone oil with a hydrogen content of 0.05-0.5 wt% and side-chain hydrogen-containing silicone oil with a hydrogen content of 0.8-1.0 wt%. This combination helps to quickly establish an initial crosslinking network and extends the reaction time to participate in the later crosslinking, resulting in more complete and uniform curing, reducing internal stress, and thus ensuring the final mechanical properties and bonding stability.

[0029] In one embodiment, the filler B comprises aluminum hydroxide B and hollow glass microspheres B.

[0030] In one embodiment, the mass ratio of aluminum hydroxide B to hollow glass microspheres B is 35-55:2-5.

[0031] In one embodiment, the mass ratio of aluminum hydroxide B to hollow glass microspheres B is 45-48:3-4.

[0032] In one embodiment, the particle size D50 of the aluminum hydroxide B is 1-40 μm.

[0033] In one embodiment, the particle size D50 of the aluminum hydroxide B is 10-20 μm.

[0034] In one embodiment, the aluminum hydroxide B has a particle size D50 of 12-15 μm, is model FR-3815, and is sourced from Hefei Zhongke Flame Retardant New Materials Co., Ltd.

[0035] In one embodiment, the hollow glass microspheres B have a particle size D50 of 10-80 μm and a density of 0.1-0.4 g / cm³. 3 .

[0036] In one embodiment, the hollow glass microspheres B have a particle size D50 of 40-50 μm and a density of 0.12-0.15 g / cm³. 3 .

[0037] In one embodiment, the hollow glass microspheres B have a particle size D50 of 40 μm and a density of 0.15 g / cm³. 3 Model number K15HSN, sourced from 3M. TM Hollow glass microspheres.

[0038] In one embodiment, the inhibitor is selected from at least one of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 2-methyl-3-butyn-2-ol, or 1-ethynyl-1-cyclohexanol. In one embodiment, the catalyst solution comprises, by weight, the following raw materials: 0.06-1 parts trifluoromethanesulfonic acid, 2.2-3 parts deionized water, and 15-18 parts anhydrous methanol.

[0039] In one embodiment, the method for preparing the tackifier includes the following steps: Tetraethyl orthosilicate, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, phenyl / methyl / vinyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane were added to a reaction vessel, heated to 60-80℃, and the catalyst solution was added dropwise over 50-60 minutes. After the addition was complete, the reaction was carried out for 2-3 hours. A neutralizing agent was added, and the mixture was stirred under vacuum for 30-40 minutes to remove low-boiling substances. The mixture was then filtered to obtain the thickener.

[0040] In one embodiment, the mass ratio of component A to component B is 1-1.5:1.

[0041] Another aspect of the present invention provides a method for preparing a low-density adhesive silicone potting compound, comprising the following steps: Vinyl polydimethylsiloxane A and filler A were added to a container and stirred to disperse to obtain a mixture. The mixture was heated and stirred under vacuum until the moisture content of the mixture was <500ppm. Platinum catalyst was added and stirred under vacuum to obtain component A. Vinyl polydimethylsiloxane B filler B is added to a container and stirred to disperse to obtain a mixture. The mixture is heated and stirred under vacuum until the moisture content of the mixture is <500ppm. Hydrogen-containing silicone oil, inhibitor and thickener are added and stirred under vacuum to obtain component B. Mix components A and B before use.

[0042] In one embodiment, the preparation method of the low-density adhesive silicone potting compound includes the following steps: Vinyl polydimethylsiloxane A and aluminum hydroxide A were added to a double planetary mixer. The stirring speed was controlled at 25-30 rpm and the dispersion speed at 400-500 rpm. The mixture was stirred and dispersed for 20-30 min to obtain a mixture. Hollow glass microspheres A were added, and the mixture was heated to 100-110℃ and stirred under vacuum for 90-120 min until the moisture content of the mixture was <500 ppm. Platinum catalyst was added, and the mixture was stirred under vacuum for 30-40 min at a speed of 35-40 rpm to obtain component A. Vinyl polydimethylsiloxane B and aluminum hydroxide B were added to a double planetary mixer. The stirring speed was controlled at 25-30 rpm and the dispersion speed at 400-500 rpm. The mixture was stirred and dispersed for 20-30 minutes to obtain a mixture. The dispersion was turned off, and the temperature was raised to 100-110℃. Hollow glass microspheres B were added and stirred until viscous. The mixture was then vacuum stirred at 100-110℃ for 90-120 minutes until the moisture content of the mixture was <500 ppm. The temperature was lowered to below 50℃, and hydrogen-containing silicone oil, inhibitors and thickeners were added. The mixture was then vacuum stirred at 35-40 rpm for 30-40 minutes to obtain component B. Mix components A and B before use.

[0043] This invention optimizes the preparation processes of components A and B, ensuring curing reliability, improving dispersion uniformity, and enhancing batch consistency to meet the needs of large-scale industrial production applications.

[0044] Beneficial effects 1. This invention provides a low-density adhesive silicone potting compound that combines low density, low viscosity, good flowability, and excellent adhesion without affecting the platinum catalytic curing efficiency, thus better meeting the needs of practical applications.

[0045] 2. This invention uses specific raw materials to prepare a tackifier through hydrolysis and condensation reaction, further controls the amount of tackifier added, and controls the viscosity of vinyl polydimethylsiloxane A and B. Without affecting the curing performance, the product provided has excellent adhesion and flowability, can fill various irregular gaps, has good adhesion to metal shells, PCB boards, etc., and is suitable for various electronic component circuit board supports, PCB board potting and new energy industry potting. It does not delaminate or crack with the circuit board substrate and has waterproof and anti-corrosion effects.

[0046] 3. This invention utilizes a compound of high-filling-content aluminum hydroxide (particle size 1-40 μm) and low-density hollow glass microspheres (particle size 10-80 μm, density 0.1-0.4 g / cm³). 3 While ensuring flame retardancy, the density of the cured adhesive was effectively reduced to 1.0 g / cm³. 3At the same time, the thixotropic properties of the product are adjusted to better meet the needs of actual applications.

[0047] 4. This invention uses a combination of end-chain hydrogen-containing silicone oil with a hydrogen content of 0.05-0.5wt% and side-chain hydrogen-containing silicone oil with a hydrogen content of 0.8-1.0wt%. This helps to quickly establish an initial crosslinking network and extends the reaction time to participate in the later crosslinking, resulting in more complete and uniform curing, reducing internal stress, and thus ensuring the final mechanical properties and bonding stability.

[0048] 5. This invention optimizes the preparation process of components A and B, ensuring curing reliability, improving dispersion uniformity, and enhancing batch consistency to meet the needs of large-scale industrial production applications. Detailed Implementation

[0049] Example 1 Example 1 of the present invention provides a low-density adhesive silicone potting compound, comprising component A and component B in a mass ratio of 1:1, and the formulation is shown in Table 1 by weight.

[0050] Table 1

[0051] The tackifier is prepared by hydrolysis and condensation reaction of the following raw materials in parts by weight: 30 parts of tetraethyl orthosilicate (Si-28), 45 parts of octamethylcyclotetrasiloxane, 15 parts of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 15 parts of phenyltrimethoxysilane, 5 parts of γ-methacryloyloxypropyltrimethoxysilane, and 17.26 parts of catalyst solution.

[0052] The catalyst solution comprises, by weight, the following raw materials: 0.06 parts trifluoromethanesulfonic acid, 2.2 parts deionized water, and 15 parts anhydrous methanol.

[0053] The method for preparing the thickener includes the following steps: Tetraethyl orthosilicate, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, phenyltrimethoxysilane, and γ-methacryloyloxypropyltrimethoxysilane were added to a reaction vessel, heated to 70°C, and a catalyst solution was added dropwise over 60 min. After the addition was complete, the reaction was carried out for 2 h. 0.5 parts by weight of calcium carbonate were added, and the mixture was stirred under vacuum for 30 min to remove low-boiling-point substances. The mixture was then filtered to obtain a thickener.

[0054] Example 1 of the present invention provides a method for preparing a low-density adhesive silicone potting compound, comprising the following steps: Vinyl polydimethylsiloxane A and aluminum hydroxide A were added to a double planetary mixer and dispersed. The stirring speed was controlled at 25 rpm and the dispersion speed at 500 rpm. The mixture was stirred and dispersed for 20 min to obtain a mixture. Hollow glass microspheres A were added, and the mixture was heated to 100℃ and stirred under vacuum for 90 min until the moisture content of the mixture was <500 ppm. Platinum catalyst was added, and the mixture was stirred under vacuum for 40 min at a speed of 35 rpm to obtain component A. Vinyl polydimethylsiloxane B and aluminum hydroxide B were added to a double planetary mixer and dispersed. The stirring speed was controlled at 25 rpm and the dispersion speed at 500 rpm. The mixture was stirred and dispersed for 20 min to obtain a mixture. The dispersion was turned off, and the temperature was raised to 100°C. Hollow glass microspheres B were added and stirred until viscous. The mixture was then stirred under vacuum at 100°C for 90 min until the moisture content of the mixture was <500 ppm. The temperature was lowered to below 50°C, and hydrogen-containing silicone oil, inhibitor and thickener were added. The mixture was stirred under vacuum at 35 rpm for 30 min to obtain component B. Mix components A and B before use.

[0055] Example 2 Example 2 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the amount of the tackifier is replaced with 2 parts by weight.

[0056] Example 3 Example 3 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the vinyl polydimethylsiloxane B2 is completely replaced with vinyl polydimethylsiloxane B1.

[0057] Example 4 Example 4 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the preparation method of the tackifier includes the following steps: tetraethyl orthosilicate, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, phenyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane are added to a reaction vessel, the temperature is raised to 80°C, a catalyst solution is added dropwise over a period of 60 min, and the reaction is carried out for 2 h after the addition is completed; 0.5 parts by weight of calcium carbonate is added and the mixture is stirred under vacuum for 30 min to remove low-boiling substances, and the tackifier is obtained by filtration.

[0058] Example 5 Example 5 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the phenyltrimethoxysilane is replaced with methyltrimethoxysilane. The preparation method of the tackifier includes the following steps: adding tetraethyl orthosilicate, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, methyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane into a reaction vessel, heating to 60°C, adding catalyst solution dropwise over a period of 60 min, and reacting for 2 h after the addition is complete; adding 0.5 parts by weight of calcium carbonate and stirring under vacuum for 30 min to remove low-boiling substances, and filtering to obtain the tackifier.

[0059] Example 6 Example 6 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the phenyltrimethoxysilane is replaced with vinyltrimethoxysilane. The preparation method of the tackifier includes the following steps: adding tetraethyl orthosilicate, octamethylcyclotetrasiloxane, 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, vinyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane into a reaction vessel, heating to 80°C, adding a catalyst solution dropwise over a period of 60 min, and reacting for 2 h after the addition is complete; adding 0.5 parts by weight of calcium carbonate and stirring under vacuum for 30 min to remove low-boiling substances, and filtering to obtain the tackifier.

[0060] Example 7 Example 7 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the tackifier is prepared by hydrolysis and condensation reaction of the following raw materials in parts by weight: 30 parts of tetraethyl orthosilicate (Si-28), 45 parts of octamethylcyclotetrasiloxane, 15 parts of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 10 parts of phenyltrimethoxysilane, 10 parts of γ-methacryloyloxypropyltrimethoxysilane, and 17.26 parts of catalyst solution.

[0061] Example 8 Example 8 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the tackifier is prepared by hydrolysis and condensation reaction of the following raw materials in parts by weight: 30 parts of tetraethyl orthosilicate (Si-28), 45 parts of octamethylcyclotetrasiloxane, 15 parts of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 5 parts of phenyltrimethoxysilane, 15 parts of γ-methacryloyloxypropyltrimethoxysilane, and 17.26 parts of catalyst solution.

[0062] Example 9 Example 9 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the type of the end-containing hydrogen silicone oil is replaced with RH-H6 and the type of the side (branch) chain hydrogen silicone oil is replaced with RH202-20L, both of which are from Zhejiang Runhe Silicone New Materials Co., Ltd.

[0063] Example 10 Example 10 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the model of vinyl polydimethylsiloxane A2 and vinyl polydimethylsiloxane B2 is replaced with RHVi1321, which is from Zhejiang Runhe Silicone New Materials Co., Ltd.

[0064] Example 11 Example 11 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the amount of end-chain hydrogen-containing silicone oil is replaced with 13 parts and the amount of side (branch) chain hydrogen-containing silicone oil is replaced with 4 parts.

[0065] Example 12 Example 12 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the tackifier is prepared by hydrolysis and condensation reaction of the following raw materials in parts by weight: 30 parts of tetraethyl orthosilicate (Si-28), 30 parts of octamethylcyclotetrasiloxane, 30 parts of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 10 parts of phenyltrimethoxysilane, 10 parts of γ-methacryloyloxypropyltrimethoxysilane, and 17.26 parts of catalyst solution.

[0066] Comparative Example 1 Comparative Example 1 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the amount of the tackifier is replaced with 0.5 parts by weight.

[0067] Comparative Example 2 Comparative Example 2 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that in the raw materials for preparing the tackifier, γ-methacryloyloxypropyltrimethoxysilane is completely replaced with phenyltrimethoxysilane.

[0068] Comparative Example 3 Comparative Example 3 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that in the raw materials for preparing the tackifier, phenyltrimethoxysilane is completely replaced with γ-aminopropyltriethoxysilane (KH550).

[0069] Comparative Example 4 Comparative Example 4 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the amount of the tackifier is replaced with 3 parts by weight.

[0070] Comparative Example 5 Comparative Example 5 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that the vinyl polydimethylsiloxane A2 and vinyl polydimethylsiloxane B2 are replaced with vinyl polydimethylsiloxane with a viscosity of 1000 mPa·s at 25°C, model RHVi1305, which is sourced from Ningbo Runhe High-Tech Materials Technology Co., Ltd.

[0071] Comparative Example 6 Comparative Example 6 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that in the raw materials for preparing the tackifier, phenyltrimethoxysilane is completely replaced with 3-isocyanopropyltrimethoxysilane.

[0072] Comparative Example 7 Comparative Example 7 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that in the raw materials for preparing the tackifier, phenyltrimethoxysilane is completely replaced with 3-mercaptopropyltrimethoxysilane.

[0073] Comparative Example 8 Comparative Example 8 of the present invention provides a low-density adhesive silicone potting compound and its preparation method. The specific implementation method is the same as that of Example 1, except that in the raw materials for preparing the tackifier, γ-methacryloyloxypropyltrimethoxysilane is completely replaced with γ-glycidoxypropyltrimethoxysilane (KH560).

[0074] Performance testing 1. Surface drying time: The test was conducted at a temperature of 25±1℃, in accordance with the specifications in GB / T 13477.5-2002: After mixing components A and B in a 1:1 weight ratio, the time was started. The surface of the potting compound was lightly touched with a clean scraper. If no compound adhered to the scraper surface, it was considered as the surface drying time. The results are shown in Table 2.

[0075] 2. Initial mixed viscosity and thixotropic index: The experiment was conducted at 25±1℃ and tested according to the specifications in GB / T 2794-2013: Component A and Component B were rapidly mixed at a weight ratio of 1:1 and then coated onto a rotational rheometer to test the viscosity. The thixotropic index was then calculated. The results are shown in Table 2.

[0076] 3. Hardness: According to ASTM D2240-15, components A and B are mixed in a 1:1 weight ratio, vacuum degassed, and poured into a 16*13*0.2cm mold. After curing on a flat vulcanizing machine (curing conditions: 100℃, 60 minutes), a sample is obtained and tested using a Shore A hardness tester. 4. Tensile strength and elongation at break: The test was conducted in accordance with GB / T 528-2009. Components A and B were mixed in a 1:1 ratio by weight, and after vacuum degassing, the mixture was poured into a 16*13*0.2cm mold. The mold was then placed on a flat vulcanizing machine for curing (curing conditions: 100℃, 60 minutes) to obtain a sample piece. The sample piece was then removed and cut into dumbbell shapes using a special cutter before being tested on a universal tensile testing machine. The results are shown in Table 2.

[0077] 5. Shear strength: Tested according to GB / T 7124-2008. Component A and B were mixed in a 1:1 weight ratio and evenly applied to different substrates with a coating size of 25*12.5*0.2mm. After complete curing (100℃, 60 minutes), the sample was tested on a universal tensile testing machine. The results are shown in Table 2. 6. Density: Tested according to GB / T 533-2008 (Method B). Component A and B were mixed in a 1:1 weight ratio, vacuum degassed, and poured into a 16*13*0.2cm mold. The mold was then cured on a flat vulcanizing machine (100℃, 60 minutes) to obtain a sample sheet. Subsequent tests were then conducted. The cured density of all examples and control examples was 1.0±0.1g / cm³. 3 .

[0078] Table 2

[0079] Note: In Comparative Examples 6, 7, and 8 in Table 2, the products provided cannot be cured after mixing components A and B. " / " indicates that the corresponding performance was not tested.

[0080] Analysis of Table 2 shows that: All embodiments 1-12 of this invention were successfully cured, with a density of 1.0 ± 0.1 g / cm³. 3 The mixture has a viscosity of less than 2000 mPa·s and a thixotropic index between 1.65 and 1.97, exhibiting good fluidity and workability.

[0081] All embodiments exhibited high shear strength for both aluminum and PCB, and the failure mode was cohesive failure, demonstrating the effectiveness of the tackifier system of this invention.

[0082] The bond strength of Comparative Example 1 (insufficient tackifier) ​​and Comparative Example 2 (lack of key polar groups in the tackifier) ​​decreased significantly, and interfacial damage occurred.

[0083] Comparative Examples 3, 6, and 7 used silanes containing amino, isocyanate, and mercapto groups, which resulted in the adhesive failing to cure, demonstrating the necessity of the raw material selection for the tackifier in this invention.

[0084] Although the adhesion of Comparative Example 4 (excessive tackifier) ​​and Comparative Example 5 (excessively high silicone oil viscosity) was acceptable, the viscosity or thixotropic index increased significantly, resulting in poor flowability, which was not conducive to potting.

[0085] Comparative Example 8 (using KH560) showed very low bond strength and poor thixotropy, demonstrating the necessity of the raw material selection for the tackifier in this invention.

Claims

1. A low-density adhesive silicone potting compound, characterized in that, It includes component A and component B, wherein component A, by mass, comprises the following raw materials: Vinyl polydimethylsiloxane A: 40-60 parts, wherein the viscosity of vinyl polydimethylsiloxane A at 25°C is 100-500 mPa·s; Platinum catalyst: 0.1-1 part; Packing material A: 40-65 parts; Component B, by mass, comprises the following raw materials: Vinyl polydimethylsiloxane B: 20-40 parts, wherein the viscosity of vinyl polydimethylsiloxane B at 25°C is 100-500 mPa·s; Hydrogen-containing silicone oil: 10-25 parts; Packing material B: 40-65 parts; Inhibitor: 0.05-0.2 parts; Tackifier: 1-2.5 parts; the tackifier is prepared by hydrolysis and condensation reaction of the following raw materials in parts by weight: 25-35 parts of tetraethyl orthosilicate, 25-50 parts of octamethylcyclotetrasiloxane, 10-30 parts of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 5-20 parts of phenyl / methyl / vinyltrimethoxysilane, 3-15 parts of γ-methacryloyloxypropyltrimethoxysilane, and 15-20 parts of catalyst solution.

2. The low-density adhesive silicone potting compound according to claim 1, characterized in that, The vinyl polydimethylsiloxane A includes vinyl polydimethylsiloxane A1 with a viscosity of 300-400 mPa·s at 25°C and vinyl polydimethylsiloxane A2 with a viscosity of 100-200 mPa·s at 25°C.

3. The low-density adhesive silicone potting compound according to claim 2, characterized in that, The mass ratio of vinyl polydimethylsiloxane A1 to vinyl polydimethylsiloxane A2 is 2-3.5:1.5-3.

4. The low-density adhesive silicone potting compound according to claim 1, characterized in that, The filler A includes aluminum hydroxide A and hollow glass microspheres A, wherein the particle size of aluminum hydroxide A is 1-40 μm and the particle size of hollow glass microspheres A is 10-80 μm.

5. The low-density adhesive silicone potting compound according to claim 4, characterized in that, The mass ratio of aluminum hydroxide A to hollow glass microspheres A is 35-55:2-5.

6. The low-density adhesive silicone potting compound according to claim 1, characterized in that, The vinyl polydimethylsiloxane B includes vinyl polydimethylsiloxane B1 with a viscosity of 300-400 mPa·s at 25°C and vinyl polydimethylsiloxane B2 with a viscosity of 100-200 mPa·s at 25°C.

7. The low-density adhesive silicone potting compound according to claim 6, characterized in that, The mass ratio of vinyl polydimethylsiloxane B1 to vinyl polydimethylsiloxane B2 is 20-30:3-10.

8. The low-density adhesive silicone potting compound according to claim 1, characterized in that, The hydrogen-containing silicone oil includes terminal hydrogen-containing silicone oil and side-chain hydrogen-containing silicone oil. The hydrogen content of the terminal hydrogen-containing silicone oil is 0.05-0.5 wt%, and the hydrogen content of the side-chain hydrogen-containing silicone oil is 0.8-1.0 wt%.

9. The low-density adhesive silicone potting compound according to claim 1, characterized in that, The inhibitor is selected from at least one of 2,4,6,8-tetramethyl-2,4,6,8-tetravinylcyclotetrasiloxane, 2-methyl-3-butyn-2-ol, or 1-ethynyl-1-cyclohexanol.

10. A method for preparing a low-density adhesive silicone potting compound according to any one of claims 1-9, characterized in that, Includes the following steps: Vinyl polydimethylsiloxane A and filler A were added to a container and stirred to disperse to obtain a mixture. The mixture was heated and stirred under vacuum until the moisture content of the mixture was <500ppm. Platinum catalyst was added and stirred under vacuum to obtain component A. Vinyl polydimethylsiloxane B and filler B are added to a container and stirred to disperse to obtain a mixture. The mixture is heated and stirred under vacuum until the moisture content of the mixture is <500ppm. Hydrogen-containing silicone oil, inhibitor and thickener are added and stirred under vacuum to obtain component B. Mix components A and B before use.

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