Dispersion method of nano heat-conducting filler, pre-dispersion liquid and epoxy glue composition

Abstract

The invention provides a nanometer heat-conducting filler dispersion method, a pre-dispersion liquid and an epoxy glue composition, the method comprises ultrasonic dispersion, and the ultrasonic dispersion sequentially comprises intermittent ultrasonic pre-dispersion and continuous ultrasonic uniform dispersion; the invention also provides a nano heat-conducting filler pre-dispersion liquid for the heat-conducting epoxy glue, the nano heat-conducting filler pre-dispersion liquid comprises the nano heat-conducting filler powder, an epoxy diluent and an antioxidant, and the weight ratio of the nano heat-conducting filler powder in the nano heat-conducting filler pre-dispersion liquid is 50-90%. Compared with the prior art, the dispersion method for the nano heat-conducting filler and the pre-dispersion liquid have the advantages that on the basis that the basic heat-conducting requirement of heat-conducting epoxy glue is met, the good storage anti-settling performance is achieved, and the good dispersion processing effect is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of thermally conductive epoxy adhesive materials, and relates to a nano thermally conductive filler dispersion method for preparing thermally conductive epoxy adhesive, a pre-dispersion liquid and a preparation method thereof, and a thermally conductive epoxy adhesive composition. Background Art

[0002] Epoxy materials have a highly cross-linked structure and low thermal conductivity, making them poor conductors of heat. They often need to be filled with thermally conductive fillers with a high filling rate to be widely used in the thermal conductivity field. However, epoxy adhesives with high thermal conductivity obtained by increasing the filling rate generally have problems such as easy sedimentation, poor processability, weak bonding strength, and high brittleness.

[0003] By adding nano-sized thermal conductive fillers, a higher thermal conductivity effect can be achieved at a lower filling rate. However, the nano-sized thermal conductive fillers are prone to agglomeration and sedimentation during use. The invention patent with patent number CN200710189891.X provides a high thermal conductivity epoxy resin nanocomposite material preparation process. Through high-speed stirring and ultrasonic oscillation, nano-ceramic particles are evenly dispersed in epoxy resin, solving the sedimentation problem of nano-ceramic particles in resin. The thermal conductive epoxy glue obtained by ultrasonic oscillation of nano-thermal conductive fillers can indeed meet the needs of products with low sedimentation requirements. However, for products that need to be stored for a long time, it is still difficult to avoid the problem of sedimentation.

[0004] Therefore, there is an urgent need for a nano thermally conductive filler and a preparation method so that the epoxy adhesive product can maintain a good anti-settling effect even in a long storage environment while satisfying the thermal conductivity effect. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, the present invention provides:

[0006] A method for dispersing nano thermally conductive fillers for thermally conductive epoxy adhesive includes ultrasonic dispersion, wherein the ultrasonic dispersion includes intermittent ultrasonic pre-dispersion and continuous ultrasonic uniform dispersion in sequence.

[0007] Furthermore, the interval time of the intermittent ultrasonic pre-dispersion is 5-10s, the dispersion time each time is 20-30s, and the total dispersion time is 0.5-1.0h.

[0008] Furthermore, the total time of continuous ultrasonic uniform dispersion is 1.5-3.0h.

[0009] A nano thermally conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive comprises nano thermally conductive filler powder, epoxy diluent and antioxidant, wherein the weight proportion of the nano thermally conductive filler powder in the nano thermally conductive filler pre-dispersion liquid is 50-90%.

[0010] Furthermore, the weight proportion of the epoxy diluent in the nano thermal conductive filler pre-dispersion liquid is 6.5-50%.

[0011] Furthermore, the weight ratio of the epoxy diluent to the nano thermal conductive filler powder is 20-100:100.

[0012] Furthermore, the weight proportion of the antioxidant in the nano thermal conductive filler pre-dispersion liquid is ≤1%.

[0013] Furthermore, the antioxidant is pentaerythritol ester.

[0014] A method for preparing the above-mentioned nano thermal conductive filler pre-dispersion liquid comprises S11. sequentially mixing nano thermal conductive filler powder, epoxy diluent, and antioxidant; S12. ultrasonic dispersion; characterized in that:

[0015] The S12. ultrasonic dispersion includes two dispersions: intermittent ultrasonic pre-dispersion and continuous ultrasonic uniform dispersion.

[0016] A thermally conductive epoxy adhesive composition comprises epoxy resin, nano thermally conductive filler pre-dispersion liquid, and epoxy curing agent; the weight proportion of the epoxy resin is 10-20%, and the weight proportion of the epoxy curing agent is 10-20%; wherein:

[0017] In the thermally conductive epoxy adhesive composition, the weight proportion of nano thermally conductive filler powder is ≥35%.

[0018] Compared with the prior art, the present invention provides a nano thermally conductive filler pre-dispersion liquid, so that the epoxy adhesive prepared by the nano thermally conductive filler can achieve good anti-settling effect under long-term storage conditions; in addition, a preparation method of the dispersion liquid is also provided to further improve the dispersion processing efficiency and antioxidant effect of the dispersion liquid. DETAILED DESCRIPTION

[0019] An embodiment of the present invention provides a method for dispersing nano thermally conductive fillers for thermally conductive epoxy adhesive, comprising ultrasonic dispersion, wherein: the ultrasonic dispersion comprises intermittent ultrasonic pre-dispersion and continuous ultrasonic uniform dispersion in sequence.

[0020] Furthermore, the interval time of the intermittent ultrasonic pre-dispersion is 5-10s, the dispersion time each time is 20-30s, and the total dispersion time is 0.5-1.0h.

[0021] Furthermore, the total time of continuous ultrasonic uniform dispersion is 1.5-3.0h.

[0022] In the preparation process of existing thermally conductive epoxy adhesives, nano thermally conductive fillers are usually added in the form of powders. To ensure thermal conductivity efficiency, the more powder filling, the better. Since the nano filler powder particles are tiny, direct addition often results in agglomeration, which is not conducive to powder dispersion. Moreover, even with auxiliary means such as ultrasonic technology, sedimentation will still become more and more significant during long-term storage. This embodiment performs pre-mixing through intermittent ultrasonic pre-dispersion and then performs uniform mixing in conjunction with subsequent continuous ultrasonic uniform dispersion, which can further reduce the risk of oxidation during the preparation process.

[0023] The embodiment of the present invention provides a nano thermally conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive, comprising nano thermally conductive filler powder, epoxy diluent, and antioxidant, wherein the weight proportion of the nano thermally conductive filler powder in the nano thermally conductive filler pre-dispersion liquid is 50-90%.

[0024] Furthermore, the weight proportion of the epoxy diluent in the nano thermal conductive filler pre-dispersion liquid is 6.5-50%.

[0025] Furthermore, the weight ratio of the epoxy diluent to the nano thermal conductive filler powder is 20-100:100.

[0026] Furthermore, in the nano thermally conductive filler pre-dispersion liquid, the weight proportion of the antioxidant in the nano thermally conductive filler pre-dispersion liquid is ≤1%.

[0027] Furthermore, the antioxidant is pentaerythritol ester.

[0028] Specifically, the nano thermally conductive filler powder is selected from insulating nano thermally conductive fillers commonly used in the art, including but not limited to any one or a combination of nano alumina, silicon dioxide, silicon carbide, aluminum nitride, and boron nitride.

[0029] Specifically, the nano thermal conductive filler powder is preferably spherical or nearly spherical in shape.

[0030] Specifically, the nano thermal conductive filler powder has a particle size range of 50-200 nm. Preferably, the powder has a particle size of 150 nm.

[0031] Specifically, the epoxy diluent is an active diluent, selected from epoxy active diluents commonly used in the art, including but not limited to 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, C12-14 fatty glycidyl ether, any one or a combination of several thereof; preferably, the epoxy diluent is C12-14 fatty glycidyl ether.

[0032] By preparing the powder into a dispersion and adding it, powder agglomeration can be effectively avoided during the production process and the dispersion efficiency can be improved to meet the long-term storage requirements. In addition, since the powder particles are fine, oxidation problems are prone to occur during high-speed continuous dispersion. This embodiment can also prevent oxidation risks by adding an appropriate amount of antioxidants.

[0033] The embodiment of the present invention further provides a method for preparing the above-mentioned nano thermal conductive filler pre-dispersion liquid, comprising S11. sequentially mixing nano thermal conductive filler powder, epoxy diluent, and antioxidant, and S12. ultrasonic dispersion; wherein:

[0034] The S12. ultrasonic dispersion includes two dispersions: intermittent ultrasonic pre-dispersion and continuous ultrasonic uniform dispersion.

[0035] Furthermore, the interval time of the intermittent ultrasonic pre-dispersion is 5-10s, the dispersion time each time is 20-30s, and the total dispersion time is 0.5-1.0h. Preferably, the intermittent ultrasonic dispersion time is 0.5h, the ultrasonic oscillation is once every 5s, each time is 20s, and the power is 500W.

[0036] Furthermore, the total time of continuous ultrasonic uniform dispersion is 1.5-3.0 hours. Preferably, the continuous ultrasonic dispersion time is 1.5 hours, and preferably, the continuous ultrasonic dispersion power is 800W.

[0037] During the preparation of the dispersion, oxidation problems are more likely to occur due to the long-term high-frequency oscillation of ultrasound. In this embodiment, pre-mixing is performed by intermittent ultrasonic pre-dispersion, and then uniform mixing is performed in conjunction with subsequent continuous ultrasonic uniform dispersion, which can further reduce the risk of oxidation during the preparation process.

[0038] The embodiment of the present invention also provides a thermally conductive epoxy adhesive composition prepared by using the above-mentioned nano thermally conductive filler pre-dispersion liquid, comprising epoxy resin, nano thermally conductive filler pre-dispersion liquid, and epoxy curing agent; the weight proportion of the epoxy resin is 10-20%, and the weight proportion of the epoxy curing agent is 10-20%; wherein:

[0039] The weight proportion of the nano thermal conductive filler powder is ≥35%.

[0040] Specifically, the epoxy resin is selected from common epoxy resin materials in the art, including but not limited to any one or a combination of epoxy resin E-44, epoxy resin E-51, epoxy resin NPER-133L and epoxy resin NPEF-170.

[0041] Specifically, the epoxy curing agent is selected from any one or a combination of polyamide curing agents, fatty amine curing agents, phenolic amine curing agents, alicyclic amine curing agents, etc. commonly used in the art; preferably, the epoxy curing agent is an anhydride modified curing agent, which is used to chemically react with the epoxy resin and form a three-dimensional network structure, including but not limited to any one or a combination of phthalic anhydride, tetrahydrophthalic anhydride, etc.

[0042] Specifically, the thermally conductive epoxy adhesive composition also contains additives commonly used in the art such as toughening agents, and the amount and process of addition can be adjusted according to product requirements, including but not limited to any one or a combination of polyurethane modified epoxy resin, nano core-shell modified resin, carboxyl-terminated liquid nitrile rubber, amino-terminated liquid nitrile rubber, and paste resin.

[0043] Example 1

[0044] Raw materials:

[0045] The nano thermal conductive filler powder is alumina (commercial model DK410-1);

[0046] The epoxy resin is bisphenol A epoxy resin, and the toughening agent is polyurethane (commercial model JEF-0211);

[0047] The epoxy curing agent is commercially available (commercial model QS-820), and the accelerator is 2-ethylimidazole.

[0048] Preparation method:

[0049] S1. 140 parts by weight of epoxy resin and 18 parts by weight of toughening agent were mixed and stirred until uniform; then, the mixture and nano-thermal conductive filler powder were added to an ultrasonic stirring mixer for intermittent ultrasonic pre-dispersion, the ultrasonic power was 500W, the total number of ultrasonic oscillations was 70 times, oscillation was performed every 5S, each oscillation time was 20S, and the total dispersion time was 30 minutes; then, the ultrasonic power was turned to 800W for continuous ultrasonic uniform dispersion, and ultrasonic oscillation was stirred for 3h; finally, vacuum degassing was performed to obtain component A;

[0050] S2. 1.0 parts by weight of 2-ethylimidazole, 420 parts by weight of thermally conductive filler powder, and 30 parts by weight of epoxy curing agent were added to an ultrasonic stirring mixer for intermittent ultrasonic pre-dispersion, with an ultrasonic power of 500 W, a total number of ultrasonic oscillations of 70 times, oscillations every 5 seconds, each oscillation time of 20 seconds, and a total dispersion time of 30 minutes; then, the ultrasonic power was turned to 800 W for continuous ultrasonic uniform dispersion, and ultrasonic oscillation was stirred for 3 hours; then, the vacuum was turned on, the temperature was raised to 80°C, and 150 parts by weight of epoxy curing agent were added again, mixed and stirred until uniform; finally, vacuum degassing was performed to obtain component B;

[0051] S3. Component A and component B are mixed in a weight ratio of 4:1 and the anti-settling performance is tested; then, the mixture is heated to 100° C. for curing and the thermal conductivity is tested.

[0052] Example 2

[0053] Raw materials:

[0054] The nano thermal conductive filler powder is alumina (commercial model DK410-1), the epoxy diluent is fatty glycidyl ether (commercial model C12-14), and the antioxidant is pentaerythritol ester (commercial model 1010);

[0055] The epoxy resin is bisphenol A epoxy resin, and the toughening agent is polyurethane (commercial model JEF-0211);

[0056] The epoxy curing agent is commercially available (commercial model QS-820), and the accelerator is 2-ethylimidazole.

[0057] Preparation method:

[0058] S1. 100 parts by weight of thermally conductive filler powder, 100 parts by weight of epoxy diluent, and 0.5 parts by weight of antioxidant were mixed; then, the mixture was transferred to an ultrasonic stirring mixer for intermittent ultrasonic pre-dispersion, the ultrasonic power was 500W, the total number of ultrasonic oscillations was 70 times, oscillation was once every 5S, each oscillation time was 20S, and the total dispersion time was 30 minutes; finally, the ultrasonic power was turned to 800W for continuous ultrasonic uniform dispersion, ultrasonic oscillation and stirring for 2h, and a nano-thermal conductive filler pre-dispersion liquid was obtained;

[0059] S2. 140 parts by weight of epoxy resin and 18 parts by weight of toughening agent were mixed and stirred until uniform; then, 420 parts by weight of the pre-dispersion of the thermally conductive nanofiller was added to the mixture and stirring was continued until uniformly mixed; finally, vacuum degassing was performed to obtain component A;

[0060] S3. 1.0 parts by weight of 2-ethylimidazole, 420 parts by weight of thermally conductive filler powder, and 30 parts by weight of epoxy curing agent were added to an ultrasonic stirring mixer for intermittent ultrasonic pre-dispersion, with an ultrasonic power of 500 W, a total number of ultrasonic oscillations of 70 times, oscillations every 5 seconds, each oscillation time of 20 seconds, and a total dispersion time of 30 minutes; then, the ultrasonic power was turned to 800 W for continuous ultrasonic uniform dispersion, and ultrasonic oscillation was stirred for 3 hours; then, the vacuum was turned on, the temperature was raised to 80°C, and 150 parts by weight of epoxy curing agent were added again, mixed and stirred until uniform; finally, vacuum degassing was performed to obtain component B;

[0061] S4. Component A and component B are mixed in a weight ratio of 4:1 and the anti-settling performance is tested; then, the mixture is heated to 100° C. for curing and the thermal conductivity is tested.

[0062] Comparative Example 1

[0063] The difference between Comparative Example 1 and Example 1 is that the thermal conductive filler in component B is added in the form of powder and is uniformly dispersed only by continuous ultrasound.

[0064] Embodiment 11, 12

[0065] The difference between Examples 11 and 12 and Example 2 lies in the weight ratio of the diluent to the nano thermally conductive filler in the nano thermally conductive filler pre-dispersion liquid.

[0066] Embodiment 21, 22

[0067] The difference between Examples 21 and 22 and Example 2 is the weight proportion of the nano thermal conductive filler powder in component B.

[0068] The materials and processes used in the embodiments and comparative examples of the present invention are shown in Table 1 below:

[0069] Table 1

[0070]

[0071] Test Method

[0072] Delamination, hardening and oxidation: Store components A and B at 40°C for 7 days respectively and observe: (1) whether delamination occurs and whether plate-like lumps appear on the bottom layer after delamination. If delamination or even hardening occurs, the anti-sedimentation property is poor; (2) whether the color turns yellow. If so, oxidation has occurred.

[0073] Thermal conductivity: Using the ASTM D 5470 heat flow steady-state method, the components A and B of the composition were mixed and injected into the mold, and then cured at 130°C for 30 minutes to obtain test samples of 26mm×26mm and thicknesses of 1, 2, and 3mm. Then, the thermal conductivity of the samples was tested at room temperature to see if it met the basic thermal conductivity requirement of ≥1W / m·k.

[0074] The test results of the embodiments of the present invention and the comparative examples are shown in Table 2:

[0075] Table 2

[0076]

[0077] It can be seen from the above embodiments, comparative examples and test results that the thermal conductivity of the thermally conductive epoxy adhesive prepared by the present invention is ≥1W / (m·K), which meets the common requirements of thermal conductivity, and also has the following features:

[0078] (1) Comparative Example 1 and Example 1 show that, when stored at 40°C for 7 days, the composition showed obvious stratification and hardening after adding powder and adopting the existing ultrasonic dispersion process, while no obvious stratification phenomenon occurred after adopting the intermittent and continuous ultrasonic dispersion process of the present invention.

[0079] (2) Further, Examples 1 and 2 show that compared with the direct addition of nano-thermal conductive filler powder to component A in Example 1, the dispersion of the present invention does not cause stratification;

[0080] (3) Furthermore, Comparative Example 1 and Examples 1 and 2 show that, compared with conventional nano-thermal conductive filler addition methods, the dispersion liquid and dispersion process of the present invention do not show signs of oxidation and yellowing;

[0081] (4) Furthermore, Examples 2, 11, and 12 show that an increase in the weight percentage of the nano-thermal conductive filler in the dispersion will lead to the occurrence of sedimentation.

[0082] (5) Furthermore, Comparative Example 2 and Example 2 show that compared with Comparative Example 1 in which component B is dispersed by conventional process, component B does not delaminate after adding modified anhydride in batches and cooperating with ultrasonic dispersion process according to the present invention.

[0083] The test results of the above embodiments and comparative examples show that the nano-thermal conductive filler dispersion method, dispersion liquid and thermal conductive epoxy adhesive composition prepared therefrom provided by the present invention have good storage anti-settling performance and anti-oxidation effect of ultrasonic vibration dispersion processing.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the protection scope of the present invention. Those skilled in the art should understand that the technical solution of the present invention can be deduced or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for dispersing nano-thermal conductive fillers for thermally conductive epoxy adhesives, comprising ultrasonic dispersion, characterized in that: The ultrasonic dispersion includes intermittent ultrasonic pre-dispersion and continuous ultrasonic uniform dispersion.

2. The method for preparing the nano thermal conductive filler pre-dispersion liquid according to claim 1, characterized in that: The interval time of the intermittent ultrasonic pre-dispersion is 5-10s, the dispersion time each time is 20-30s, and the total dispersion time is 0.5-1.0h.

3. The method for preparing the nano thermal conductive filler pre-dispersion liquid according to claim 2, characterized in that: The total time of continuous ultrasonic uniform dispersion is 1.5-3.0h.

4. A nano thermally conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive, comprising nano thermally conductive filler powder, epoxy diluent, and antioxidant, characterized in that: The weight proportion of the nano thermally conductive filler powder in the nano thermally conductive filler pre-dispersion liquid is 50-90%.

5. The nano-thermal conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive according to claim 4, characterized in that: The weight proportion of the epoxy diluent in the nano thermal conductive filler pre-dispersion liquid is 6.5-50%.

6. The nano-thermal conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive according to claim 5, characterized in that: The weight ratio of the epoxy diluent to the nano thermal conductive filler powder is 20-100:

100.

7. The nano thermally conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive according to claim 6, characterized in that: The weight proportion of the antioxidant in the nano thermal conductive filler pre-dispersion liquid is ≤1%.

8. The nano-thermal conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive according to claim 7, characterized in that: The antioxidant is pentaerythritol ester.

9. A method for preparing a nano thermally conductive filler pre-dispersion liquid for thermally conductive epoxy adhesive as claimed in claim 4, comprising S11. sequentially mixing nano thermally conductive filler powder, epoxy diluent, and antioxidant; S12. ultrasonic dispersion; characterized in that: The S12. ultrasonic dispersion includes two dispersions: intermittent ultrasonic pre-dispersion and continuous ultrasonic uniform dispersion.

10. A thermally conductive epoxy adhesive composition, comprising epoxy resin, nano thermally conductive filler pre-dispersion liquid, and epoxy curing agent; the epoxy resin accounts for 10-20% by weight, and the epoxy curing agent accounts for 10-20% by weight; characterized in that: The weight proportion of the nano thermal conductive filler powder is ≥35%.

Images