Hydrophobic heat-conducting structural adhesive and preparation method thereof

Abstract

The invention discloses a hydrophobic heat-conducting structural adhesive and a preparation method thereof, belongs to the technical field of heat-conducting structural adhesives, and aims to solve the problems that the preparation steps of the existing polyurethane heat-conducting structural adhesive are complicated, the steps can be improved, the preparation reaction time of the polyurethane heat-conducting structural adhesive is shortened, and the preparation steps are simplified. The hydrophobic fumed silica and the catalyst are added after the component A and the component B are mixed, the hydrophobic fumed silica provides thixotropy for the mixed solution, regulates the rheological property of the glue solution and guarantees the dispersion stability of the heat-conducting filler, and the catalyst is combined to accelerate the reaction and promote the full reaction of active groups in the component A and the component B; through the arrangement of the component A and the component B, the main agent of the component A of the heat-conducting structural adhesive is polyether polyol, the main agent of the component B is diphenylmethane diisocyanate, a heat-conducting filler is matched to serve as a main raw material, the component A and the component B are mixed and then subjected to reaction curing through-NCO and-OH, the preparation is carried out according to the steps, and repeated operation of the same component does not exist.

Description

Technical Field

[0001] This invention relates to the field of thermally conductive structural adhesives, and particularly to a hydrophobic thermally conductive structural adhesive and its preparation method. Background Technology

[0002] Thermally conductive structural adhesives are functional adhesives that combine bonding strength and thermal conductivity. They have a wide range of applications, covering multiple fields such as electronic devices, power modules, and LED lighting. With the continuous miniaturization and high performance of modern electronic devices, the requirements for thermal management are increasing. Developing structural adhesives that can achieve excellent thermal conductivity while connecting devices has become a key technology for solving thermal management challenges.

[0003] A polyurethane thermally conductive structural adhesive and its preparation method are disclosed in authorization announcement number CN118064102A. The adhesive comprises component A and component B. Component A, by mass parts, includes the following raw materials: 12-15 parts modified castor oil, 28-32 parts castor oil-modified polyester polyol, 1-2 parts coupling agent, 40-55 parts modified thermally conductive and flame-retardant filler, and 2-4 parts hydrophobic fumed silica. Component B, by mass parts, includes the following raw materials: 2 parts isocyanate... The polyurethane thermally conductive structural adhesive of this application contains 5-30 parts of a coupling agent, 1-2 parts of a modified thermally conductive and flame-retardant filler, 40-55 parts of a hydrophobic fumed silica, 2-4 parts of a dehydrating agent, and 0.5-1 parts of a dehydrating agent. Although hydrophobic fumed silica is added to both component A and component B of the polyurethane thermally conductive structural adhesive, the preparation steps are complicated. Meanwhile, the dehydrating agent is mainly used to act on the polyester polyol, which can change the addition steps of the additives, reduce the reaction time of the polyurethane thermally conductive structural adhesive, and simplify the preparation steps.

[0004] To address the aforementioned problems, a hydrophobic thermally conductive structural adhesive and its preparation method are proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a hydrophobic thermally conductive structural adhesive and its preparation method, which solves the problem that existing polyurethane thermally conductive structural adhesives, although containing hydrophobic fumed silica, are added to both component A and component B, resulting in complicated preparation steps. At the same time, the dehydrating agent is mainly used to act on the polyester polyol, which can change the addition steps of the additives, reduce the reaction time of the polyurethane thermally conductive structural adhesive preparation, and simplify the preparation steps.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a hydrophobic thermally conductive structural adhesive and its preparation method, comprising component A and component B, wherein the mass ratio of component A to component B is 10:3, and by mass parts: Component A comprises the following raw materials: 20-30 parts of polyether diol, 10-20 parts of polyether triol, 0.2-2 parts of silane coupling agent, 2-3 parts of modified acrylic resin, 0.1-1.0 parts of dehydrating agent, 2-10 parts of chain extender, 30-80 parts of thermally conductive filler, 5-10 parts of flame retardant, and 0.1-0.5 parts of antioxidant; by weight. Component B comprises the following raw materials: 30-40 parts of diphenylmethane diisocyanate and 1-5 parts of reactive diluent; The hydrophobic thermally conductive structural adhesive is prepared by mixing component A and component B with 5-10 parts of hydrophobic fumed silica and 1-2 parts of catalyst.

[0007] Another technical solution proposed in this invention: Provides a hydrophobic thermally conductive structural adhesive and its preparation method, comprising the following steps: S1: Preparation of component A: Component A is prepared according to the corresponding mass fractions. The main component of component A is polyether polyol. S2: Preparation of component B: Component B is prepared according to the corresponding mass fractions. The main agent of component B is diphenylmethane diisocyanate. S3: Mixing of components A and B: When mixing components A and B, add hydrophobic fumed silica and catalyst and stir thoroughly; S4: Glue filling and sealing: The well-reacted glue is sent into the glue filling machine and sealed after filling.

[0008] The preparation of component A includes the following steps: S11: Base material mixing: Add the metered polyether polyol, modified acrylic resin, silane coupling agent and dehydrating agent into the reactor according to the mass ratio, heat and stir under vacuum to remove water; S12: Functional additive mixing: Stepwise mixing and diffusion of dehydrating agents, chain extenders, thermally conductive fillers, flame retardants, and antioxidants; S13: Degassing and storage: Vacuum degassing, dry and sealed container storage.

[0009] The mixing of functional additives includes the following steps: S121: Adding dehydrating agent: After the mixture temperature drops below 60℃, add the dehydrating agent and stir. S122: Adding remaining additives: Add the metered chain extender, thermally conductive filler, flame retardant, and antioxidant, and stir while keeping warm.

[0010] The preparation of component B includes the following steps: S21: MDI melt: Solid diphenylmethane diisocyanate is melted and filtered to remove impurities; S22: Mixing and Adjustment: Add liquid MDI to a dry reactor, heat up and add active diluent while stirring; S23: Filtered storage: Filtered by a screen, stored in a sealed container away from light.

[0011] The mixing of components A and B includes the following steps: S31: Additive addition: Mix components A and B at a mass ratio of 10:3, add hydrophobic fumed silica, and stir to disperse; S32: Catalyst addition: Add catalyst and stir the reaction; S33: Vacuum degassing: Vacuum degassing.

[0012] Potting and sealing includes the following steps: S41: Pot life determination: Confirm the pot life of the adhesive and plan the amount of adhesive to be applied; S42: Glue dispensing: Automatic glue dispensing machine dispensing glue.

[0013] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention provides a hydrophobic thermally conductive structural adhesive and its preparation method. By mixing component A and component B and adding hydrophobic fumed silica and a catalyst, the hydrophobic fumed silica provides thixotropy to the mixture, regulating the rheological properties of the adhesive and ensuring the dispersion stability of the thermally conductive filler. Hydrophobicity is a key characteristic of silica. By modifying the surface with a silane coupling agent to reduce hydrophilicity, the water resistance and damp heat resistance of the adhesive layer are directly improved. Combined with the catalyst, the reaction is accelerated, promoting the full reaction of active groups (-OH and -NCO) in components A and B, reducing unreacted residual groups, thereby optimizing the adhesive layer performance. This solves the problem that existing polyurethane thermally conductive structural adhesives, although adding hydrophobic fumed silica, do not have a complex preparation process as they are added to both components A and B.

[0014] 2. This invention provides a hydrophobic thermally conductive structural adhesive and its preparation method. Through the setting of components A and B, the main agent of component A is polyether polyol, and the main agent of component B is diphenylmethane diisocyanate. Combined with thermally conductive fillers as the main raw materials, components A and B are mixed and cured via a reaction between -NCO and -OH. The preparation is carried out step-by-step, without repetitive operations on the same components, thus solving the problems of existing polyurethane thermally conductive structural adhesives, reducing reaction time, and simplifying preparation steps. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the process of the present invention. Detailed Implementation

[0016] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] In order to solve existing technical problems, such as Figure 1 As shown, the following preferred technical solutions are provided: A hydrophobic thermally conductive structural adhesive comprises a component A and a component B in a mass ratio of 10:3. By mass, component A comprises the following raw materials: 20-30 parts polyether diol, 10-20 parts polyether triol, 0.2-2 parts silane coupling agent, 2-3 parts modified acrylic resin, 0.1-1.0 parts dehydrating agent, 2-10 parts chain extender, 30-80 parts thermally conductive filler, 5-10 parts flame retardant, and 0.1-0.5 parts antioxidant. By mass, component B comprises the following raw materials: 30-40 parts diphenylmethane diisocyanate and 1-5 parts reactive diluent. The hydrophobic thermally conductive structural adhesive is prepared by mixing component A and component B with 5-10 parts hydrophobic fumed silica and 1-2 parts catalyst.

[0018] Specifically, the main component of this thermally conductive structural adhesive is polyether polyol in component A and diphenylmethane diisocyanate in component B. Thermally conductive fillers are also used as the main raw materials. After mixing components A and B, the adhesive is cured through a reaction between -NCO and -OH. Hydrophobic fumed silica is added during the mixing of components A and B. Its core function is to regulate the rheological properties of the adhesive solution, while also positively influencing the physical and mechanical properties and environmental stability of the adhesive layer. It is a key additive that meets the construction and performance requirements of thermally conductive structural adhesives. A catalyst is also added during mixing, its core function being to regulate the rate and process of the curing reaction, ensuring that the adhesive cures within the expected time and ultimately forms an adhesive layer with excellent mechanical, thermal conductivity, and adhesive properties.

[0019] To further illustrate the above embodiments, the present invention also provides an implementation scheme: a hydrophobic thermally conductive structural adhesive and its preparation method, comprising the following steps: Step 1: Preparation of Component A: Prepare Component A according to the corresponding mass proportions. The main component of Component A is polyether polyol. Step 2: Preparation of Component B: Component B is prepared according to the corresponding mass proportions. The main agent of Component B is diphenylmethane diisocyanate. Step 3: Mixing components A and B: When mixing components A and B, add hydrophobic fumed silica and catalyst and stir thoroughly; Step 4: Glue Pouring and Sealing: Pour the reacted glue into the transfer container, and then send the glue into the glue pouring machine through the transfer container. After glue pouring, seal the machine.

[0020] The preparation of component A includes the following steps: Step 1: Base material mixing: Add the metered polyether polyol, modified acrylic resin, silane coupling agent and dehydrating agent into the reaction vessel according to the mass ratio. Under the condition of dispersion and stirring, heat to 60-80℃, turn on the vacuum, the vacuum degree is 0.01-300Pa, and stir to remove water for 2 hours. This will initially remove the moisture from the raw materials and prevent the reaction with component B MDI to generate CO2 bubbles, which would damage the density of the adhesive layer. At the same time, it will provide a stable liquid matrix for the subsequent addition of solid additives. Step Two: Mixing of Functional Additives: The dehydrating agent, chain extender, thermally conductive filler, flame retardant, and antioxidant are mixed and diffused in stages to prevent agglomeration from affecting thermal conductivity or flame retardant properties. Step 3: Degassing and storage: Vacuum degassing for 20-30 minutes while stirring at low speed, cool to room temperature, then pack into a dry, sealed container and store in a cool place to remove air introduced during dispersion and prevent component A from absorbing moisture or separating during storage.

[0021] The mixing of functional additives includes the following steps: Step 1: Adding the dehydrating agent: Wait until the temperature of the mixture drops below 60℃ to avoid high temperature affecting the stability of the dehydrating agent. Then add the dehydrating agent and stir for 10-20 minutes. Step 2: Adding remaining additives: Add the metered chain extender, thermally conductive filler, flame retardant, and antioxidant. Under dispersion and stirring conditions, stir for 4-6 hours while maintaining the temperature at 60-70℃ until the material is fully diffused.

[0022] The preparation of component B includes the following steps: Step 1: MDI melting: Solid diphenylmethane diisocyanate is melted at 50-60℃ to prepare liquid MDI for later use. Impurities are removed by filtration through a filter cloth to ensure the activity of MDI and avoid side reactions caused by impurities. Step 2: Mixing and Adjustment: Add liquid MDI to a dry reaction vessel, heat to 40-50℃, slowly add reactive diluent while stirring, stir for 30 minutes until uniform, add reactive diluent to reduce the viscosity of component B, making it easier to mix with component A in subsequent use; Step 3: Filtration and Storage: Filter the product through a screen to remove mechanical impurities, then store it in a sealed container away from light to prevent impurities from affecting the uniformity of curing and to maintain the -NCO content of MDI.

[0023] The mixing of components A and B includes the following steps: Step 1: Additive Addition: The mass ratio of component A to component B is 10:3. Add hydrophobic fumed silica and stir to disperse. The hydrophobic fumed silica provides thixotropy to the adhesive, regulates the rheological properties of the adhesive, and ensures the dispersion stability of the thermally conductive filler. Hydrophobicity is a key characteristic of silica. By modifying the surface with a silane coupling agent, hydrophilicity is reduced, directly improving the water resistance and damp heat resistance of the adhesive layer. Step 2: Catalyst addition: Add catalyst, stir the reaction, and allow it to cool naturally. After 4-6 hours, the reactants will cool to 30-40℃ and form a gel. The catalyst accelerates the reaction, promotes the full reaction of active groups (-OH and -NCO) in components A and B, reduces unreacted residual groups, and thus optimizes the performance of the adhesive layer. Step 3: Vacuum degassing: Vacuum degassing for 5-10 minutes, stop when no bubbles overflow from the adhesive. This removes air introduced during mixing, prevents bubbles from forming in the adhesive layer after pouring, and ensures thermal conductivity and mechanical properties.

[0024] Potting and sealing includes the following steps: Step 1: Determine the pot life: Confirm the pot life of the adhesive. At 25℃, it is usually 1-4 hours. The pot life decreases as the temperature increases. Plan the amount of adhesive to be poured. Step 2: Glue application: Glue is applied using an automatic glue application machine.

[0025] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0026] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A hydrophobic heat-conducting structural adhesive, comprising A component and B component, the mass ratio of the A component and the B component being 10:3, in terms of mass fraction: The A component comprises the following raw materials: polyether diol 20-30 parts, polyether triol 10-20 parts, silane coupling agent 0.2-2 parts, modified acrylic resin 2-3 parts, water removal agent 0.1-1.0 parts, chain extender 2-10 parts, heat-conducting filler 30-80 parts, flame retardant 5-10 parts, antioxidant 0.1-0.5 parts; in terms of mass fraction; The B component comprises the following raw materials: diphenyl methane diisocyanate 30-40 parts, active diluent 1-5 parts; The A component and the B component are mixed with 5-10 parts of hydrophobic fumed silica and 1-2 parts of catalyst to form the hydrophobic heat-conducting structural adhesive.

2. A process for preparing the hydrophobic thermally conductive structural adhesive according to claim 1, characterized in that, The method comprises the following steps: S1: preparing the A component: configuring the A component according to the corresponding mass fraction, and the main agent of the A component is polyether polyol; S2: preparing the B component: configuring the B component according to the corresponding mass fraction, and the main agent of the B component is diphenyl methane diisocyanate; S3: mixing the A component and the B component: adding hydrophobic fumed silica and catalyst when mixing the A component and the B component, and fully stirring; S4: glue sealing: sending the reacted glue into a glue filling machine, and sealing after glue filling.

3. A process for preparing the hydrophobic thermally conductive structural adhesive as claimed in claim 2, wherein, The preparation of the A component comprises the following steps: S11: mixing the base material: putting the metered polyether polyol, modified acrylic resin, silane coupling agent and water removal agent into a reaction kettle according to the mass ratio, heating and vacuum stirring to remove water; S12: mixing the functional additives: stepwise mixing and diffusion of the water removal agent, chain extender, heat-conducting filler, flame retardant and antioxidant; S13: degassing and storage: vacuum degassing and dry sealing barrel storage.

4. A process for preparing the hydrophobic thermally conductive structural adhesive as claimed in claim 3, wherein, The functional additive mixing comprises the following steps: S121: adding the water removal agent: adding the water removal agent and stirring when the temperature of the mixture drops below 60℃; S122: adding the remaining additives: adding the metered chain extender, heat-conducting filler, flame retardant and antioxidant, and heat preservation stirring.

5. A method for preparing the hydrophobic thermally conductive structural adhesive as described in claim 2, characterized in that, The preparation of the B component comprises the following steps: S21: MDI melting: melting the solid diphenyl methane diisocyanate, and filtering impurities; S22: mixing and adjusting: adding the liquid MDI into the dry reaction kettle, heating, adding the active diluent and stirring; S23: filtering and storing: filtering through the filter screen, and storing in the sealed barrel in the dark.

6. A process for preparing the hydrophobic thermally conductive structural adhesive according to claim 1, characterized in that, The mixing of the A component and the B component comprises the following steps: S31: adding the additives: mixing according to the mass ratio of 10:3 of the A component and the B component, adding the hydrophobic fumed silica, and stirring and dispersing; S32: adding the catalyst: adding the catalyst and stirring and reacting; S33: vacuum degassing: vacuum degassing.

7. A method for preparing the hydrophobic thermally conductive structural adhesive as described in claim 1, characterized in that, The glue sealing comprises the following steps: S41: determining the pot life: determining the pot life of the glue solution, and planning the glue filling amount; S42: glue filling: glue filling by the automatic glue filling machine.

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