High-filling low-viscosity acrylate type heat-conducting adhesive and preparation method thereof

Abstract

The invention discloses a high-filling low-viscosity acrylate type heat-conducting adhesive and a preparation method thereof, the performance of the heat-conducting adhesive is synergistically regulated and controlled through compression of filler spacing by a forced phase separation technology and surface modification of a double-bond-containing long-carbon-chain silane coupling agent, so that the heat-conducting adhesive has relatively high heat conductivity and good flowability, the filling rate is greater than 93 wt%, and the thermal conductivity is greater than 93wt%. The viscosity of the heat-conducting adhesive is less than 235 Pa.s under high filling, the heat-conducting adhesive has good fluidity, the traditional cognition that high filling must have high viscosity in the prior art is broken through, good fluidity is maintained while unprecedented heat-conducting performance is achieved, and the core requirements of next-generation electronic equipment, electric automobiles and high-power batteries are met. Meanwhile, the heat-conducting adhesive has good shear strength, and a better industrial implementation solution is provided for a high-heat-conductivity interface material. And the preparation process is simple and pollution-free, and has an excellent industrial production application prospect.

Description

Technical Field

[0001] The present invention relates to a highly filled thermally conductive adhesive and a preparation method thereof, and in particular to a highly filled low-viscosity acrylate thermally conductive adhesive prepared based on a forced phase separation technology and a preparation method thereof. Background Art

[0002] With the rapid development of electronic devices towards high power density and miniaturization, efficient thermal management technology has become a key bottleneck restricting device reliability. Advanced application areas represented by microelectronics packaging, high-power LED heat dissipation and new energy vehicle battery thermal management have put forward an urgent demand for thermal interface thermal conductive materials with high thermal conductivity. Thermal conductive adhesives are usually composed of resins and thermal conductive fillers. They can effectively bond the heating components of electronic devices to the heat sink for a long time, providing stable heat dissipation. Since resins have high phonon scattering, resulting in low thermal conductivity, the existing technology increases the thermal conductivity of thermal conductive adhesives by adding a large amount of thermal conductive fillers.

[0003] In this context, highly filled thermally conductive adhesives are a commonly used physical modification path to significantly improve the thermal conductivity of materials by introducing large amounts of highly thermally conductive fillers such as boron nitride, aluminum oxide, and aluminum nitride. However, while such highly filled systems enhance thermal conductivity, they often easily cause an exponential increase in the viscosity of the system, leading to a sharp deterioration in the fluidity of the colloid, and producing process defects such as residual pores and poor interface wetting during coating, potting, and compression molding. What is more prominent is that the compromise solutions adopted in the existing technology to improve processability, such as reducing the filler content or adding diluents, essentially destroy the effective construction of the thermal conductive network, resulting in a decrease in thermal conductivity and seriously weakening the practical application value of the material. This contradictory relationship between thermal conductivity and processing performance has become a core technical problem that restricts the large-scale application of highly filled thermally conductive adhesives in the field of precision electronic heat dissipation.

[0004] Existing technologies primarily focus on reducing the viscosity of thermally conductive adhesives by surface modifying fillers. For example, Chinese patents CN116814188A and CN104673160A both pre-treat the filler surface before filling, adjusting the viscosity by optimizing the filler's dispersibility and compatibility with the resin matrix. However, surface modification has limited effectiveness in reducing the viscosity of thermally conductive adhesives, and excessive addition of modifiers can disrupt the filler's thermal conductivity network, increasing thermal resistance and leading to reduced thermal conductivity.

[0005] In view of the above reasons, how to break through the rheological limitations caused by high filler filling, achieve controllable adjustment of colloid viscosity while maintaining excellent thermal conductivity, and then optimize the practical application prospects of thermal conductive adhesives has become a key issue that needs to be urgently solved in this field. Summary of the Invention

[0006] In order to address the deficiencies of the prior art, the purpose of the present invention is to prepare a modified multi-scale alumina high-filled thermal conductive adhesive through forced phase separation technology, which solves the problem of poor fluidity of high-filled thermal conductive adhesive in the prior art and improves the thermal conductivity and strength of the material.

[0007] In order to achieve the above objectives, the present invention adopts the following technical solutions:

[0008] The present invention first discloses a highly filled, low-viscosity acrylate-based thermally conductive adhesive, which is prepared by mixing an acrylate reaction solution and multi-scale modified alumina into a slurry and then using a forced phase separation technique. The mass ratio of the acrylate reaction solution to the multi-scale modified alumina is 1:(3-6);

[0009] The acrylate reaction solution comprises: 80-120 parts by mass of a monofunctional acrylate monomer, 8-12 parts by mass of a multifunctional acrylate monomer, 0.2-1 parts by mass of an initiator, and 0.05-0.1 parts by mass of a stabilizer;

[0010] The multi-scale modified alumina comprises: 80-120 parts by mass of a multi-scale alumina mixture and 1-5 parts by mass of a silane coupling agent containing a double bond and a long carbon chain.

[0011] Preferably, the aforementioned monofunctional acrylate monomer is one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate.

[0012] Preferably, the multifunctional acrylate monomer is one or more of ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate.

[0013] More preferably, the initiator is a peroxide initiator or an azo initiator, and the stabilizer is one of hydroquinone, methylhydroquinone or p-benzoquinone.

[0014] Further preferably, the multi-scale alumina mixture comprises small-scale alumina with an average particle size of 1-10 microns and large-scale alumina with an average particle size of 60-80 microns; in the multi-scale alumina mixture, the mass ratio of small-scale alumina is 10-30%.

[0015] Still more preferably, the large-scale alumina and the small-scale alumina inside the aforementioned thermal conductive adhesive form a gear meshing shape, forming a criss-cross thermal conductive network structure, which greatly improves the thermal conductivity.

[0016] The present invention also discloses a method for preparing the aforementioned high-filled, low-viscosity acrylate-based thermally conductive adhesive, comprising the following steps:

[0017] (1) Preparation of multi-scale modified alumina

[0018] Add 80-120 parts by mass of a multi-scale alumina mixture and 1-5 parts by mass of a silane coupling agent containing a double bond long carbon chain into a reaction kettle, heat to 70-90° C., react for 3-5 hours, and cool to room temperature to obtain a multi-scale modified alumina;

[0019] (2) Preparation of acrylate reaction solution

[0020] Add 80-120 parts by mass of a monofunctional acrylate monomer, 8-12 parts by mass of a multifunctional acrylate monomer, 0.2-1 parts by mass of an initiator, and 0.05-0.1 parts by mass of a stabilizer into a reaction kettle, and stir at room temperature for 30-60 minutes to obtain a transparent acrylate reaction solution;

[0021] (3) Preparation of multi-scale modified alumina / acrylate slurry

[0022] First, 100 parts by mass of the acrylate reaction solution prepared in step (2) above is added to a stirred tank, stirring is started, and 300-600 parts by mass of the multi-scale modified alumina prepared in step (1) above is slowly added over 10-30 minutes, and stirring is continued for 30-60 minutes to obtain a multi-scale modified alumina / acrylate slurry;

[0023] (4) Preparation of high-filled, low-viscosity acrylic thermal conductive adhesive based on forced phase separation technology

[0024] The multi-scale modified alumina / acrylate slurry prepared in the above step (3) is settled at 25-50° C. for 30-60 hours, and the supernatant is separated by starvation dropwise addition to obtain a high-filling, low-viscosity acrylate thermal conductive adhesive.

[0025] Further preferably, the long carbon chain silane coupling agent containing double bonds in the aforementioned step (1) is homemade, and the specific preparation method is as follows: 100 parts by mass of a long carbon chain diene and 0.15-0.25 parts by mass of a platinum catalyst are added to a four-necked flask, and 80-110 parts by mass of triethoxysilane are added dropwise at 75-90° C. by a starvation dropwise addition method, and the addition time is controlled to be 1-3 hours. After the addition is completed, the temperature is continued to be raised to 90-120° C., and the reaction is carried out for 3-5 hours, followed by cooling to room temperature to obtain a long carbon chain silane coupling agent containing double bonds. The long carbon chain coupling agent can make the modified filler have good hydrophobicity, facilitate the sedimentation of the modified filler in the acrylate system, and increase the filler filling amount.

[0026] More preferably, the long carbon chain diene is one of 1,10-undecadiene, 1,11-dodecadiene, 1,12-tridecadiene or 1,13-tetradecadiene.

[0027] The present invention is beneficial in that:

[0028] (1) The forced phase separation technology of the present invention cooperates with the modification of multi-scale alumina to reduce the distance between particles. The large and small scale alumina form a gear meshing shape, forming a crisscrossing heat conduction network inside, which greatly improves the thermal conductivity. The thermal conductivity of the prepared high-filled low-viscosity acrylate thermal conductive adhesive is greater than 3.8W·m -1 ·K -1 , which is significantly improved compared with the thermal conductive adhesive prepared by direct blending.

[0029] (2) The present invention uses a silane coupling agent containing a double bond and a long carbon chain to modify the multi-scale modified alumina, which is used together with the acrylate reaction solution as a raw material. The coupling agent forms a chemical bridge between the multi-scale alumina and the acrylate matrix, minimizing interfacial phonon scattering and enabling dense packing of the filler without agglomeration. Moreover, due to the large difference in polarity between the multi-scale modified alumina and the acrylate reaction solution, it can accelerate phase separation, thereby achieving a high filling effect. Furthermore, the long carbon chain coupling agent can make the modified filler have good hydrophobicity, making it easy for the modified filler to settle in the acrylate system, further increasing the filler filling amount. In addition, the double bond of the coupling agent can copolymerize with the acrylic monomer, thereby further improving the strength of the thermal conductive adhesive.

[0030] (3) The present invention prepares a highly filled thermally conductive adhesive based on forced phase separation technology, with a mass filling rate of >93wt%. Moreover, the thermally conductive adhesive still has a certain fluidity under high filling, and its viscosity is <235Pa·s, indicating that the dispersion of the filler is significantly improved after modification, the agglomeration phenomenon is reduced, and the viscosity is correspondingly reduced, breaking the traditional cognition that "high filling must have high viscosity", and providing an industrially feasible solution for high thermal conductive interface materials, which can better meet the processing requirements in actual production application scenarios.

[0031] (4) The preparation method of the present invention has a simple process, is green and pollution-free, and has excellent industrial production prospects. It can be used in the cooling of electronic equipment, playing the dual role of bonding and rapid heat dissipation, and is the core requirement of the next generation of electronic equipment, electric vehicles and high-power batteries. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic diagram of the principle of the forced phase separation technology of the present invention;

[0033] Figure 2 is a cross-sectional scanning electron microscope (SEM) image of Example 1 after curing;

[0034] Figure 3 This is a cross-sectional scanning electron microscope (SEM) image of Comparative Example 1 after curing;

[0035] Figure 4 are infrared thermal images of Examples 1-3 and Comparative Examples 1-2;

[0036] Figure 5 1-3 and comparative example 1-2;

[0037] Figure 6 It is the thermogravimetric curve graph of Example 1-3. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Unless otherwise specified in the present invention, all raw materials used are commercially available and there is no restriction on the purchase route.

[0039] Example 1

[0040] (1) Preparation of silane coupling agent containing double bond long carbon chain

[0041] 100 parts by mass of a long carbon chain diene and 0.15 parts by mass of a platinum catalyst were added into a four-necked flask, and 110 parts by mass of triethoxysilane were added dropwise at 90°C by a starvation dropwise method. The addition time was controlled within 3 hours. After the addition was completed, the temperature was continued to rise to 120°C, and the mixture was reacted for 5 hours and then cooled to room temperature to obtain a long carbon chain silane coupling agent containing double bonds.

[0042] (2) Preparation of multi-scale modified alumina

[0043] 10 parts by mass of alumina with an average particle size of 10 microns, 90 parts by mass of alumina with an average particle size of 60 microns, and 1 part by mass of the above-prepared silane coupling agent containing a long carbon chain with double bonds were added to the reactor, the temperature was raised to 70°C, the reaction was carried out for 5 hours, and the reaction was cooled to room temperature to obtain multi-scale modified alumina.

[0044] (3) Preparation of acrylate reaction solution

[0045] 40 parts by mass of lauryl methacrylate, 40 parts by mass of hydroxyethyl methacrylate, 8 parts by mass of trimethylolpropane trimethacrylate, 0.2 parts by mass of azobisisobutyronitrile, and 0.05 parts by mass of hydroquinone were added to a reactor and stirred at room temperature for 40 minutes to obtain a transparent acrylate reaction solution.

[0046] (4) Preparation of multi-scale modified alumina / acrylate slurry

[0047] First, 100 parts by mass of the acrylate reaction solution prepared above was added to a stirring kettle, stirring was started, and 300 parts by mass of multi-scale modified alumina was slowly added within 10 minutes. Stirring was continued for 30 minutes to obtain a modified alumina / acrylate slurry.

[0048] (5) Preparation of high-filled low-viscosity acrylic thermal conductive adhesive based on forced phase separation technology

[0049] like Figure 1 As shown, the multi-scale modified alumina / acrylate slurry prepared above was allowed to settle at 50° C. for 30 hours, and the supernatant was separated by forced phase separation technology to obtain a highly filled, low-viscosity acrylate thermal conductive adhesive.

[0050] Example 2

[0051] (1) Preparation of silane coupling agent containing double bond long carbon chain

[0052] 80 parts by mass of 1,11-dodecadiene and 0.2 parts by mass of platinum catalyst were added to a four-necked flask, and 90 parts by mass of triethoxysilane were added dropwise at 80°C using a starvation dropwise addition method. The addition time was controlled within 2 hours. After the addition was completed, the temperature was continued to rise to 100°C, and the mixture was reacted for 4 hours and then cooled to room temperature to obtain a silane coupling agent containing a long carbon chain with a double bond.

[0053] (2) Preparation of multi-scale modified alumina

[0054] Add 20 parts by mass of alumina with an average particle size of 5 microns, 80 parts by mass of alumina with an average particle size of 70 microns, and 3 parts by mass of the above-prepared silane coupling agent containing a long carbon chain with double bonds into the reactor, heat to 80°C, react for 4 hours, and cool to room temperature to obtain multi-scale modified alumina.

[0055] (3) Preparation of acrylate reaction solution

[0056] 40 parts by mass of hexanediol dimethacrylate, 60 parts by mass of ethylene glycol dimethacrylate, 10 parts by mass of pentaerythritol trimethacrylate, 0.5 parts by mass of azobisisobutyronitrile, and 0.08 parts by mass of methylhydroquinone were added to a reactor and stirred at room temperature for 50 minutes to obtain an acrylate reaction solution.

[0057] (4) Preparation of multi-scale modified alumina / acrylate slurry

[0058] First, 100 parts by mass of the acrylate reaction solution prepared above was added to a stirring kettle, stirring was started, and 500 parts by mass of multi-scale modified alumina was slowly added within 20 minutes. Stirring was continued for 40 minutes to obtain a modified alumina / acrylate slurry.

[0059] (5) Preparation of high-filled low-viscosity acrylic thermal conductive adhesive based on forced phase separation technology

[0060] The multi-scale modified alumina / acrylate slurry prepared above was allowed to settle at 45° C. for 45 hours, and the supernatant was separated by forced phase separation technology to obtain a highly filled, low-viscosity acrylate thermal conductive adhesive.

[0061] Example 3

[0062] (1) Preparation of silane coupling agent containing double bond long carbon chain

[0063] 120 parts by mass of 1,13-tetradecadiene and 0.25 parts by mass of platinum catalyst were added into a four-necked flask, and 80 parts by mass of triethoxysilane were added dropwise at 75°C by starvation dropwise addition method. The addition time was controlled within 1 hour. After the addition was completed, the temperature was continued to rise to 90°C, and the mixture was reacted for 5 hours and then cooled to room temperature to obtain a silane coupling agent containing a long carbon chain with a double bond.

[0064] (2) Preparation of multi-scale modified alumina

[0065] Add 30 parts by mass of alumina with an average particle size of 1 micron, 70 parts by mass of alumina with an average particle size of 70 microns, and 5 parts by mass of the above-prepared silane coupling agent containing a long carbon chain with double bonds into the reactor, heat to 90°C, react for 3 hours, and cool to room temperature to obtain multi-scale modified alumina.

[0066] (3) Preparation of acrylate reaction solution

[0067] 60 parts by mass of hydroxypropyl methacrylate, 60 parts by mass of isooctyl methacrylate, 12 parts by mass of ethylene glycol dimethacrylate, 1 part by mass of benzoyl peroxide, and 0.1 part by mass of p-benzoquinone were added to a reactor, and stirred at room temperature for 60 minutes to obtain a transparent acrylate reaction solution.

[0068] (4) Preparation of multi-scale modified alumina / acrylate slurry

[0069] First, 100 parts by mass of the acrylate reaction solution prepared above was added to a stirring kettle, stirring was started, and 600 parts by mass of multi-scale modified alumina was slowly added over 30 minutes. Stirring was continued for 60 minutes to obtain an alumina / acrylate slurry.

[0070] (5) Preparation of high-filled low-viscosity acrylic thermal conductive adhesive based on forced phase separation technology

[0071] The multi-scale modified alumina / acrylate slurry prepared above was allowed to settle at 25° C. for 60 hours, and the supernatant was separated by forced phase separation technology to obtain a highly filled, low-viscosity acrylate thermal conductive adhesive.

[0072] Comparative Example 1

[0073] (1) Preparation of silane coupling agent containing double bond long carbon chain

[0074] 100 parts by mass of a long carbon chain diene and 0.15 parts by mass of a platinum catalyst were added into a four-necked flask, and 110 parts by mass of triethoxysilane were added dropwise at 90°C by a starvation dropwise method. The addition time was controlled within 3 hours. After the addition was completed, the temperature was continued to rise to 120°C, and the mixture was reacted for 5 hours and then cooled to room temperature to obtain a long carbon chain silane coupling agent containing double bonds.

[0075] (2) Preparation of multi-scale modified alumina

[0076] 10 parts by mass of alumina with an average particle size of 10 microns, 90 parts by mass of alumina with an average particle size of 60 microns, and 1 part by mass of the above-prepared silane coupling agent containing a long carbon chain with double bonds were added to the reactor, the temperature was raised to 70°C, the reaction was carried out for 5 hours, and the reaction was cooled to room temperature to obtain multi-scale modified alumina.

[0077] (3) Preparation of acrylate reaction solution

[0078] 40 parts by mass of lauryl methacrylate, 40 parts by mass of hydroxyethyl methacrylate, 8 parts by mass of trimethylolpropane trimethacrylate, 0.2 parts by mass of azobisisobutyronitrile, and 0.05 parts by mass of hydroquinone were added to a reactor and stirred at room temperature for 40 minutes to obtain a transparent acrylate reaction solution.

[0079] (4) Preparation of multi-scale modified alumina / acrylate slurry

[0080] First, 100 parts by mass of the acrylate reaction solution prepared above was added to the stirring kettle, stirring was started, and 900 parts by mass of the multi-scale modified alumina was slowly added within 10 minutes. Stirring was continued for 30 minutes to obtain a modified multi-scale modified alumina / acrylate thermal conductive adhesive.

[0081] Comparative Example 2

[0082] (1) Preparation of acrylate reaction solution

[0083] 40 parts by mass of lauryl methacrylate, 40 parts by mass of hydroxyethyl methacrylate, 8 parts by mass of trimethylolpropane trimethacrylate, 0.2 parts by mass of azobisisobutyronitrile, and 0.05 parts by mass of hydroquinone were added to a reactor and stirred at room temperature for 40 minutes to obtain a transparent acrylate reaction solution.

[0084] (2) Preparation of multi-scale alumina / acrylate slurry

[0085] First, 100 parts by mass of the acrylate reaction solution prepared above was added to a stirring kettle, and stirring was started. Within 10 minutes, 30 parts by mass of alumina with an average particle size of 10 microns and 270 parts by mass of alumina with an average particle size of 60 microns were slowly added. Stirring was continued for 30 minutes to obtain an alumina / acrylate slurry.

[0086] (3) Preparation of high-filled, low-viscosity acrylic thermal conductive adhesive based on forced phase separation technology

[0087] The multi-scale modified alumina / acrylate slurry prepared above was allowed to settle at 50° C. for 30 hours, and the supernatant was separated by forced phase separation technology to obtain a highly filled, low-viscosity acrylate thermal conductive adhesive.

[0088] Structural characterization and performance testing

[0089] The thermal conductive adhesives of Examples 1-3 and Comparative Examples 1-2 (after complete curing) were subjected to structural characterization and performance testing.

[0090] (1) Scanning electron microscopy (SEM)

[0091] Figure 2 and Figure 3 The cross-sectional SEM images of Example 1 and Comparative Example 1 are shown respectively. From the comparison between the two, it can be seen that the forced phase separation technology can make the filler particles more evenly distributed, such as Figure 2 As shown in Figure 1, the distance between particles is significantly reduced, and the small balls cluster around the large balls, forming a state of meshing of large and small gears. Figure 3 As shown, the filler particles are unevenly distributed, with small alumina particles not tightly wrapped around large alumina particles, resulting in a large number of gaps. This leads to a high thermal resistance in the product. This confirms that the forced phase separation technology of the present invention has a direct and effective effect on increasing the filler filling rate and forming an efficient thermal conductive network.

[0092] (2) Thermal conductivity test

[0093] First, the heat transfer capacity is tested. The testing method is: place the cured samples of the same thickness on a heating platform at 80°C, and use an infrared thermal imager to record the temperature changes on the sample surface.

[0094] Figure 4It is an infrared thermal imaging image of the upper surface of Examples 1-3 and Comparative Examples 1-2 within 300s. It can be seen from the figure that at 300s, the upper surface temperature of Examples 1-3 is all greater than 58°C, while the upper surface temperature of Comparative Examples 1 and 2 is only 39.9°C and 46.5°C. It can be seen that the thermal conductivity coefficients of Examples 1-3 are higher than those of Comparative Examples 1 and 2, that is, the thermal conductive adhesives of Examples 1-3 exhibit more excellent thermal conductivity. It can be seen that the thermal conductivity of Example 1 of the forced phase separation technology is significantly higher than that of Comparative Example 1 of direct blending, which further illustrates the positive role of forced phase separation technology in constructing an efficient thermal conductive network. In addition, the thermal conductivity of the thermal conductive adhesive filled with multi-scale modified alumina (Examples 1-3) is significantly improved compared to the unmodified alumina thermal conductive adhesive (Comparative Example 2), which shows that after modification, the thermal resistance between the filler and the resin is reduced, and the thermal conductivity is thereby improved.

[0095] Furthermore, the thermal conductivity of the sample was tested using a thermal conductivity meter according to the American standard "ASTM-D5470" for quantitative characterization. The test results are shown in Table 1.

[0096] (3) Viscosity test

[0097] The viscosity was tested using a rheometer with shear rate changes, and the results are shown in Figure 5 .from Figure 5 It can be seen that the product prepared by forced phase separation (Example 1) has a lower viscosity at a higher fill rate than the product prepared by direct mixing (Comparative Example 1). Similarly, the viscosity of Example 1 is lower than that of Comparative Example 2, demonstrating that the modified filler significantly improves dispersibility, reduces agglomeration, and correspondingly reduces viscosity. Therefore, forced phase separation technology and surface modification can synergistically adjust the viscosity of the thermally conductive adhesive to better meet processing requirements.

[0098] (4) Shear strength test

[0099] Furthermore, the shear strength of the thermal adhesive was tested using the following method: using a single lap joint specimen, the newly mixed thermal adhesive was applied to two aluminum plates with an overlap size of 12.5 mm × 25.0 mm, and the test was performed after complete curing.

[0100] The test results are shown in Table 1. The shear strengths of Examples 1-3 are all ≥3.80 MPa, while that of Comparative Example 2 is only 1.34 MPa. This indicates that after the double bond groups are grafted onto the filler, they can undergo copolymerization with the acrylic monomer, enhancing cohesion and thus greatly improving the shear strength.

[0101] (5) Thermogravimetric testing

[0102] The thermogravimetric test was performed using a microcomputer thermobalance with a test temperature of room temperature to 650°C and a heating rate of 10°C / min. Figure 6The thermogravimetric curves of Examples 1-3 are shown. The final stable residual mass ratio is the filler mass ratio. It can be seen that the filler mass ratios of Examples 1-3 are all greater than 93wt%. The specific values ​​are shown in Table 1 below.

[0103]

[0104] Table 1 Thermal conductivity and viscosity results of thermally conductive adhesives of Examples 1-3 and Comparative Examples 1-2

[0105] As can be seen from the table above, the present invention, based on the forced phase separation technology and the modification effect of multi-scale alumina, gives the thermal conductive adhesive both a high filler ratio and low viscosity. The filler mass ratio of Examples 1-3 is greater than 93wt% and the viscosity is less than 235Pa·s, while the viscosity of Comparative Examples 1 and 2 is as high as 541-569Pa·s at a filling rate of 90wt%, indicating that the preparation process of the present invention can effectively reduce the viscosity. In Comparative Example 2, where the multi-scale alumina is not modified with a silane coupling agent, the filling rate after forced phase separation is less than 90wt%. This shows that the long carbon chain modification makes the polarity difference between the filler and the acrylate reaction solution larger, promoting the effect of phase separation, thereby achieving a high filling effect.

[0106] In summary, the present invention is based on the process of forced phase separation technology and cooperates with a homemade multi-scale alumina filling modified by a long carbon chain silane coupling agent containing double bonds to obtain a multi-scale alumina high-filling thermal conductive adhesive. The thermal conductive adhesive has high thermal conductivity and good fluidity, breaking through the mutually exclusive limitations of high thermal conductive filler load and processing fluidity, and providing a solution to the problem of the contradiction between thermal conductivity and processing performance of high-filling systems. In addition, the preparation method is simple and has prospects for industrial production. It can be applied to the field of electronic heat dissipation, such as high-power LEDs, microelectronic packaging and other fields, and has good application prospects.

[0107] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any form, and any technical solutions obtained by equivalent replacement or equivalent transformation fall within the scope of protection of the present invention.

Claims

1. A highly filled, low viscosity acrylate thermally conductive adhesive, characterized in that: The acrylate reaction solution and multi-scale modified alumina are mixed into a slurry and then prepared by forced phase separation technology, wherein the mass ratio of the acrylate reaction solution to the multi-scale modified alumina is 1:(3-6); The acrylate reaction solution comprises: 80-120 parts by mass of a monofunctional acrylate monomer, 8-12 parts by mass of a multifunctional acrylate monomer, 0.2-1 parts by mass of an initiator, and 0.05-0.1 parts by mass of a stabilizer; The multi-scale modified alumina comprises: 80-120 parts by mass of a multi-scale alumina mixture and 1-5 parts by mass of a silane coupling agent containing a double bond and a long carbon chain.

2. The highly filled, low viscosity acrylate thermally conductive adhesive according to claim 1, characterized in that: The monofunctional acrylate monomer is one or more of methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, isooctyl (meth)acrylate, lauryl (meth)acrylate, hydroxyethyl (meth)acrylate, and hydroxypropyl (meth)acrylate.

3. The highly filled, low viscosity acrylate thermally conductive adhesive according to claim 1, characterized in that: The multifunctional acrylate monomer is one or more of ethylene glycol di(meth)acrylate, diethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, and pentaerythritol tri(meth)acrylate.

4. The highly filled, low viscosity acrylate thermally conductive adhesive according to claim 1, characterized in that: The initiator is a peroxide initiator or an azo initiator.

5. The highly filled, low viscosity acrylate thermally conductive adhesive according to claim 1, characterized in that: The stabilizer is one of hydroquinone, methylhydroquinone or p-benzoquinone.

6. The highly filled, low viscosity acrylate thermally conductive adhesive according to claim 1, characterized in that: The multi-scale alumina mixture comprises small-scale alumina with an average particle size of 1-10 microns and large-scale alumina with an average particle size of 60-80 microns; in the multi-scale alumina mixture, the mass ratio of small-scale alumina is 10-30%.

7. The high-filled, low-viscosity acrylate thermally conductive adhesive according to claim 6, characterized in that: The large-scale alumina and small-scale alumina inside the thermal conductive adhesive form a gear meshing shape, forming a criss-cross thermal conductive network structure.

8. The method for preparing a high-filling, low-viscosity acrylate thermally conductive adhesive according to claim 1, wherein: The steps include: (1) Preparation of multi-scale modified alumina Add 80-120 parts by mass of a multi-scale alumina mixture and 1-5 parts by mass of a silane coupling agent containing a double bond long carbon chain into a reaction kettle, heat to 70-90° C., react for 3-5 hours, and cool to room temperature to obtain a multi-scale modified alumina; (2) Preparation of acrylate reaction solution Add 80-120 parts by mass of a monofunctional acrylate monomer, 8-12 parts by mass of a multifunctional acrylate monomer, 0.2-1 parts by mass of an initiator, and 0.05-0.1 parts by mass of a stabilizer into a reaction kettle, and stir at room temperature for 30-60 minutes to obtain a transparent acrylate reaction solution; (3) Preparation of multi-scale modified alumina / acrylate slurry First, 100 parts by mass of the acrylate reaction solution prepared in step (2) above is added to a stirred tank, stirring is started, and 300-600 parts by mass of the multi-scale modified alumina prepared in step (1) above is slowly added over 10-30 minutes, and stirring is continued for 30-60 minutes to obtain a multi-scale modified alumina / acrylate slurry; (4) Preparation of high-filled, low-viscosity acrylic thermal conductive adhesive based on forced phase separation technology The multi-scale modified alumina / acrylate slurry prepared in the above step (3) is settled at 25-50° C. for 30-60 hours, and the supernatant is separated by starvation dropwise addition to obtain a high-filling, low-viscosity acrylate thermal conductive adhesive.

9. The method for preparing a high-filling, low-viscosity acrylate thermally conductive adhesive according to claim 8, characterized in that: The silane coupling agent containing a long carbon chain with a double bond in step (1) is homemade, and its preparation method is as follows: 100 parts by mass of a long carbon chain diene and 0.15-0.25 parts by mass of a platinum catalyst are added into a four-necked flask, 80-110 parts by mass of triethoxysilane are added dropwise at 75-90° C. by a starvation dropwise addition method, the dropwise addition time is controlled within 1-3 hours, and after the dropwise addition is completed, the temperature is continued to be raised to 90-120° C., the reaction is carried out for 3-5 hours, and then the mixture is cooled to room temperature to obtain the silane coupling agent containing a long carbon chain with a double bond.

10. The method for preparing a high-filling, low-viscosity acrylate thermally conductive adhesive according to claim 9, characterized in that: The long carbon chain diene is one of 1,10-undecadiene, 1,11-dodecadiene, 1,12-tridecadiene or 1,13-tetradecadiene.

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