High-thermal-conductivity bi-component flame-retardant pouring sealant and preparation method thereof

Abstract

The invention belongs to the technical field of pouring sealants, and particularly discloses a high-thermal-conductivity two-component flame-retardant pouring sealant and a preparation method thereof.The two-component pouring sealant comprises a component A and a component B. The two-component pouring sealant is characterized in that a novel multifunctional composite filler is adopted, aluminum nitride serves as a core of the filler, and the surface of the filler is coated with a zinc oxide shell layer through a hydrothermal method; a core-shell structure is formed, and phosphorus-nitrogen synergistic effect is further grafted on the surface of a shell layer through silane coupling reaction. The composite filler is combined with an organic silicon matrix through chemical bonding, and an efficient heat-conducting network and an intrinsic flame-retardant barrier are constructed in a system. According to the pouring sealant disclosed by the invention, the heat conductivity coefficient is greater than or equal to 3.0 W / (m.K) and the flame retardant property of UL94 V-0 level is realized while the excellent flowability is maintained, and the filler is good in settling resistance and excellent in comprehensive performance, so that the pouring sealant is particularly suitable for pouring protection of high-power-density electronic components.

Description

Technical Field

[0001] This invention belongs to the field of potting compound technology, and relates to a high thermal conductivity two-component flame-retardant potting compound and its preparation method. Background Technology

[0002] As electronic devices evolve towards higher power density and miniaturization, increasingly stringent requirements are being placed on the thermal conductivity and flame retardant properties of potting compounds. Traditional approaches typically improve performance by physically blending high proportions of multifunctional composite fillers (such as alumina and aluminum nitride) with flame-retardant fillers (such as aluminum hydroxide and magnesium hydroxide). However, this method has inherent drawbacks: poor compatibility between the filler and matrix leads to high interfacial thermal resistance, limiting the improvement in thermal conductivity; high filler content results in a sharp increase in system viscosity, making processing difficult; and physical blends are prone to migration and precipitation, affecting long-term reliability.

[0003] Existing improvement solutions, such as CN113150656A which uses a compound of spherical alumina and boron nitride to improve flowability, suffer from insufficient flame retardancy; CN115322549A improves dispersibility by modifying magnesium hydroxide, but the improvement in thermal conductivity is not significant. Furthermore, most patents (such as prior art documents CN108219741A and CN118895095A) focus on the physical compounding and simple modification of fillers, failing to fundamentally solve the synergistic problem between "high thermal conductivity" and "high flame retardancy" at the molecular level, nor effectively reduce the interfacial thermal resistance between the filler and the matrix.

[0004] Therefore, developing a novel potting compound that can achieve strong interfacial bonding between the filler and the matrix while simultaneously imparting intrinsic thermal conductivity and flame retardant properties has become a pressing technical challenge in this field. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by providing a high thermal conductivity two-component flame-retardant potting compound and its preparation method. This potting compound, through the introduction of an innovative multifunctional composite filler, achieves efficient construction of thermal conductivity pathways and intrinsic flame-retardant function, thereby obtaining extremely high thermal conductivity and reliable flame-retardant rating at a relatively low viscosity. Based on this objective, this invention provides a high thermal conductivity two-component flame-retardant potting compound, comprising component A and component B; Component A comprises the following raw materials by weight: 10-50 parts vinyl silicone oil, 5-20 parts dimethyl silicone oil, 20-100 parts multifunctional composite filler, and 0.1-2 parts platinum catalyst; Component B comprises the following raw materials by weight: 10-50 parts vinyl silicone oil, 5-20 parts dimethyl silicone oil, 5-20 parts hydrogen-containing silicone oil, 20-100 parts multifunctional composite filler, and 0.01-1 parts inhibitor.

[0006] Preferably, the vinyl silicone oil has a viscosity of 100-3000 mPa·s at room temperature, including but not limited to 100 mPa·s, 500 mPa·s, 1000 mPa·s, 1500 mPa·s, and 3000 mPa·s, more preferably 1000 mPa·s. The vinyl content in the vinyl silicone oil is 0.1%-2% by mass.

[0007] Preferably, the hydrogen-containing silicone oil is one or more of end-hydrogen-containing silicone oil or side-hydrogen-containing silicone oil; more preferably, it is a mixture of end-hydrogen-containing silicone oil and side-hydrogen-containing silicone oil in a ratio of 3:1, wherein the mass content of hydrogen is 0.1-2%.

[0008] Preferably, the inhibitor is one or more of tetramethyltetravinylcyclotetrasiloxane, polyvinylpolysiloxane, 3,5-dimethyl-1-hexyn-3-ol, methylvinylcyclotetrasiloxane, and 3-methyl-1-butyn-3-ol.

[0009] Preferably, the multifunctional composite filler is a core-shell structure filler, which consists of an aluminum nitride (AlN) core, a zinc oxide (ZnO) shell covering the core, and phosphorus-nitrogen synergy grafted onto the shell surface.

[0010] Preferably, the phosphorus-nitrogen synergy is the reaction product of DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) and vinyltriethoxysilane.

[0011] Preferably, the mass ratio of the aluminum nitride core to the zinc oxide shell is (2:1) to (4:1); the amount of phosphorus-nitrogen synergistic grafting accounts for 1% to 5% of the total mass of the composite filler.

[0012] Preferably, the platinum catalyst is selected from one or more of the following: a platinum catalyst coordinated with tetrahydrofuran, an alcoholic solution of chloroplatinic acid, and a platinum catalyst coordinated with divinyltetramethylsiloxane, more preferably an alcoholic solution of chloroplatinic acid.

[0013] Preferably, in actual use, the mass ratio of component A to component B is 1-2:1, more preferably 1:1, 1.5:1, 2:1, and even more preferably 1:1.

[0014] The present invention also discloses a method for preparing the two-component potting compound, the steps of which are as follows: Preparation of multifunctional composite fillers: a. Aluminum nitride micropowder was dispersed in a 0.5 mol / L zinc nitrate aqueous solution at a solid-liquid ratio of 1:10 and ultrasonically dispersed for 30 minutes. The suspension was then transferred to a high-pressure reactor and hydrothermally reacted at 180°C for 12 hours. After the reaction, the mixture was allowed to cool naturally, filtered, washed repeatedly with deionized water and ethanol, and dried at 110°C for 6 hours to obtain AlN@ZnO core-shell powder.

[0015] b. Under nitrogen protection, DOPO and a silane coupling agent are added to a three-necked flask equipped with a reflux condenser at a molar ratio of 1:1. The silane coupling agent is one of vinyltriethoxysilane, vinyltrimethoxysilane, or γ-(methacryloyloxy)propyltrimethoxysilane. The mixture is heated to 120°C and reacted for 4 hours until no phosphine gas is produced, thus obtaining the DOPO-silane coupling agent.

[0016] c. Disperse AlN@ZnO core-shell powder in toluene, add 30% (by weight of powder) of DOPO-silane coupling agent, and reflux at 110°C for 8 hours. After the reaction, centrifuge, wash three times with toluene, and vacuum dry at 80°C to constant weight to obtain the multifunctional composite filler.

[0017] Component A: First, mix and stir silicone oil and multifunctional composite filler, heat and dehydrate to obtain base material, then add coupling agent, crosslinking agent and catalyst, mix and stir, and vacuum to obtain component A; Component B: Vinyl silicone oil, dimethyl silicone oil, hydrogen-containing silicone oil, multifunctional composite filler, and inhibitor are mixed and stirred, and then vacuum degassed to obtain component B.

[0018] Preferably, the vacuum degree is above -0.09 MPa and the mixing time is above 30 min.

[0019] The silane coupling agent is selected from one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and γ-(methacryloyloxy)propyltrimethoxysilane. The present invention has the following beneficial effects: This invention fundamentally changes the physical blending mode of fillers in traditional potting compounds by designing a multifunctional composite filler with a "core-shell-molecular brush" structure. The aluminum nitride core provides basic high thermal conductivity, the zinc oxide shell improves interfacial phonon matching, and the phosphorus-nitrogen grafts through chemical bonding achieve the "intrinsicization" of flame retardant function. The filler achieves "anchoring" of the filler through the addition reaction between the vinyl groups at the ends and the organosilicon matrix, which greatly reduces the interfacial thermal resistance, constructs a continuous and efficient thermal conduction network, and endows the potting compound system with excellent thermal conductivity (≥3.0 W / (m·K)).

[0020] This invention ingeniously introduces highly efficient flame-retardant elements into the filler surface through chemical bonding, constructing a multi-layered flame-retardant barrier. During combustion, this system synergistically exerts its flame-retardant effect through the gas-phase flame-retardant mechanism (free radical capture) of DOPO derivatives and the char formation effect of the condensed phase, meeting the stringent UL 94 V-0 flame-retardant standard while avoiding traditional migration and precipitation problems.

[0021] The strong interfacial bonding between the filler and the matrix effectively prevents sedimentation, the system viscosity is controllable, and the flowability is good, facilitating potting application. The chemically bonded structure ensures the interfacial stability of the potting compound under thermal shock, resulting in a long service life.

[0022] The technical solution of this invention has the following properties: ASTM D5470 value greater than 2.5 W / (mK), more preferably greater than 3.5 W / (mK); flame retardancy rating / UL94 V-0; hardness / Shore A greater than 50; tensile strength greater than 2.0 MPa, more preferably greater than 3.0 MPa; and settlement stability at 80℃ with no settlement after 7 days. Detailed Implementation

[0023] The embodiments of the present invention will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are only for illustrating the present invention and should not be regarded as limiting the scope of the present invention.

[0024] Example 1: Preparation of multifunctional composite fillers Synthesis of AlN@ZnO core-shell precursor: 20g of aluminum nitride powder with an average particle size of 5μm was dispersed in 200mL of 0.5mol / L zinc nitrate aqueous solution and stirred vigorously for 30 minutes. The suspension was then transferred to a high-pressure reactor and hydrothermally reacted at 180℃ for 12 hours. After the reaction, the mixture was allowed to cool naturally, filtered, washed repeatedly with deionized water and ethanol, and dried at 110℃ for 6 hours to obtain AlN@ZnO core-shell powder. Synthesis of DOPO-silane coupling agent: Under nitrogen protection, 21.6g (0.1mol) of DOPO and 22.0g (0.1mol) of vinyltriethoxysilane were added to a three-necked flask equipped with a reflux condenser. The mixture was heated to 120℃ and reacted for 4 hours until no phosphine gas was produced, yielding a pale yellow viscous liquid, which was the DOPO-silane coupling agent. Grafting modification of multifunctional composite filler: 10g of the above AlN@ZnO core-shell powder was dispersed in 100mL of toluene, and 3g of the DOPO-silane coupling agent synthesized in step 2 was added. The mixture was refluxed at 110℃ for 8 hours. After the reaction, the mixture was centrifuged, washed three times with toluene to remove the physically adsorbed coupling agent, and finally vacuum dried at 80℃ to constant weight to obtain the final multifunctional composite filler, denoted as FN. Example 2: Preparation of potting compound components A and B Component A formulation (parts by weight): Vinyl silicone oil (viscosity 1000 mPa·s): 30 parts Dimethyl silicone oil: 10 parts FN: 60 servings Platinum catalyst (isopropanol solution of chloroplatinic acid, Pt content 3000 ppm): 0.5 parts Component B formulation (parts by weight): Vinyl silicone oil (viscosity 1000 mPa·s): 30 parts Dimethyl silicone oil: 10 parts Hydrogen-containing silicone oil (hydrogen content 0.8%): 15 parts FN: 50 servings Inhibitor (methylvinylcyclotetrasiloxane): 0.05 parts Preparation process: Add the raw materials of components A and B to a planetary mixer and mix them for 35 minutes at a revolution speed of 20 Hz and a rotation speed of 30 Hz.

[0025] The mixed rubber compound was transferred to a vacuum degassing machine and degassed at -0.098 MPa for 5 minutes until no visible air bubbles were found in the rubber compound.

[0026] Discharge the materials separately, seal and package them to obtain component A and component B.

[0027] Example 3 The only difference from Example 2 is that the amount of FN in component A is 80 parts, and the amount of FN in component B is 70 parts. Everything else is the same as in Example 2.

[0028] Example 4 The only difference from Example 2 is that the amount of FN in component A is 40 parts, and the amount of FN in component B is 30 parts. Everything else is the same as in Example 2.

[0029] Comparative Example 1 The same formulation and process as in Example 2 were used, except that FN was replaced with an equal mass of a physical mixture of untreated aluminum nitride and zinc oxide (AlN:ZnO mass ratio = 3:1).

[0030] Comparative Example 2 The same formulation and process as in Example 2 were used, the only difference being that FN was replaced with an equal mass of aluminum nitride filler that had only undergone surface modification with vinyltriethoxysilane but without constructing a core-shell structure and without grafting phosphorus-nitrogen synergy. The preparation method was as follows: 10 g of aluminum nitride powder with an average particle size of 5 μm was dispersed in 100 mL of toluene, 3 g of vinyltriethoxysilane was added, and the mixture was refluxed at 110 °C for 8 hours. After the reaction, the mixture was centrifuged, washed three times with toluene, and vacuum dried at 80 °C to constant weight to obtain the control filler.

[0031] Example 5 The same formulation and process as in Example 2 were used, with the only difference being that the silane coupling agent used in step b when preparing the multifunctional composite filler was γ-(methacryloyloxy)propyltrimethoxysilane.

[0032] The two-component thermally conductive potting compound products obtained in the above examples and comparative examples were mixed evenly with component A to component B at a mass ratio of 1:1 and then used for potting high-power LED modules. The performance of the two-component thermally conductive potting compound was tested according to relevant standards, and the results are shown in Table 1.

[0033] Table 1

[0034] As can be seen from the data in the table above, the two-component thermally conductive potting compound based on a core-shell structure multifunctional filler in this invention has a higher thermal conductivity and reliable V-0 flame retardancy. Simultaneously, the filler exhibits excellent anti-settling properties and a moderate surface drying time, facilitating application. Comparative Example 1 uses a simple physical mixture filler, which has poor thermal conductivity and flame retardancy and is prone to settling. Comparative Example 2 uses a common silane-modified filler, whose performance is improved but still far inferior to the core-shell structure-grafted phosphorus-nitrogen synergistic filler of this invention. Comparative Example 3 uses different silane coupling agents, and its overall performance is better than Comparative Example 2 but slightly lower than the preferred embodiment of this invention (Example 2). This indicates that the choice of silane coupling agent affects the effectiveness of this invention, with vinyltriethoxysilane showing better performance in this system.

[0035] The above embodiments describe preferred embodiments of the present invention, but the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other way. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention. Therefore, the protection scope of this patent should be determined by the appended claims.

Claims

1. A high thermal conductivity two-component flame-retardant potting compound, comprising component A and component B, characterized in that... ； Component A comprises the following raw materials by weight: 10-50 parts vinyl silicone oil, 5-20 parts dimethyl silicone oil, 20-100 parts multifunctional composite filler, and 0.1-2 parts platinum catalyst; Component B comprises the following raw materials by weight: 10-50 parts vinyl silicone oil, 5-20 parts dimethyl silicone oil, 5-20 parts hydrogen-containing silicone oil, 20-100 parts multifunctional composite filler, and 0.01-1 parts inhibitor.

2. The high thermal conductivity two-component flame-retardant potting compound according to claim 1, characterized in that: The vinyl silicone oil has a viscosity of 100-3000 mPa·s at room temperature, and the vinyl content in the vinyl silicone oil is 0.1%-2% by mass.

3. The high thermal conductivity two-component flame-retardant potting compound according to claim 1, characterized in that: The hydrogen-containing silicone oil is one or more of end-hydrogen-containing silicone oil or side-hydrogen-containing silicone oil, wherein the mass content of hydrogen is 0.1-2%.

4. The high thermal conductivity two-component flame-retardant potting compound according to claim 1, characterized in that: The inhibitor is one or more of tetramethyltetravinylcyclotetrasiloxane, polyvinylpolysiloxane, 3,5-dimethyl-1-hexyn-3-ol, methylvinylcyclotetrasiloxane, and 3-methyl-1-butyn-3-ol.

5. The high thermal conductivity two-component flame-retardant potting compound according to claim 1, characterized in that: The multifunctional composite filler is a core-shell structured filler, which consists of an aluminum nitride core, a zinc oxide shell covering the core, and phosphorus-nitrogen synergy grafted onto the shell surface.

6. The high thermal conductivity two-component flame-retardant potting compound according to claim 1, characterized in that: The phosphorus-nitrogen synergy is the reaction product of DOPO (9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) and a silane coupling agent; the silane coupling agent is one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and γ-(methacryloyloxy)propyltrimethoxysilane.

7. The high thermal conductivity two-component flame-retardant potting compound according to claim 6, characterized in that: The mass ratio of the aluminum nitride core to the zinc oxide shell is (2:1) to (4:1); the amount of phosphorus-nitrogen synergistic grafting accounts for 1% to 5% of the total mass of the composite filler.

8. The two-component potting compound according to claim 1, characterized in that: The platinum catalyst is selected from one or more of the following: a platinum catalyst coordinated with tetrahydrofuran, an alcoholic solution of chloroplatinic acid, and a platinum catalyst coordinated with divinyltetramethylsiloxane.

9. The method for preparing the two-component potting compound according to any one of claims 1 to 8, characterized in that: Component A: Vinyl silicone oil, dimethyl silicone oil, multifunctional composite filler, and platinum catalyst are mixed and stirred, and then degassed under vacuum to obtain component A; Component B: Vinyl silicone oil, dimethyl silicone oil, hydrogen-containing silicone oil, multifunctional composite filler, and inhibitor are mixed and stirred, and then vacuum degassed to obtain component B; The two-component potting compound is obtained by mixing component A and component B.

10. The method for preparing the two-component potting compound according to claim 9, characterized in that, Preparation of multifunctional composite fillers: a. Aluminum nitride micro powder was dispersed in a zinc salt solution, and a zinc oxide shell was grown on the surface of aluminum nitride through a hydrothermal reaction to obtain an AlN@ZnO core-shell structure precursor; b. React DOPO with a silane coupling agent under an inert atmosphere to synthesize a DOPO-silane coupling agent; wherein the silane coupling agent is one or more of vinyltriethoxysilane, vinyltrimethoxysilane, and γ-(methacryloyloxy)propyltrimethoxysilane; c. The AlN@ZnO precursor obtained in step a and the DOPO-silane coupling agent obtained in step b are refluxed in an organic solvent. After washing and drying, the multifunctional composite filler is obtained.

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