A high thermal conductivity polyurethane potting adhesive and its preparation method

Abstract

The present invention relates to the technical field of potting adhesives, and particularly relates to a highly thermally conductive polyurethane potting adhesive and a preparation method thereof. The raw materials for its preparation include: component A and component B; the raw materials for component A include MDI, a first plasticizer, a first thermally conductive filler, and a first dispersant; the raw materials for component B include polyols, a second plasticizer, a second thermally conductive filler, and an auxiliary agent; both the first thermally conductive filler and the second thermally conductive filler are compositions including BN nanosheets, spherical alumina, and diamond powder; the average particle size of the BN nanosheets is larger than the average particle size of the spherical alumina; the average particle size of the spherical alumina is 2 - 12 μm; the spherical alumina at least includes first spherical alumina and second spherical alumina; the average particle size of the first spherical alumina is larger than the average particle size of the second spherical alumina. The polyurethane potting adhesive prepared by the present invention has low viscosity, good flowability, and high thermal conductivity, and has higher practical value.

Description

Technical Field

[0001] The present invention relates to the technical field of potting adhesives, and particularly relates to a high thermal conductivity polyurethane potting adhesive and a preparation method thereof. Background Art

[0002] With the rapid development of the electronics industry, the application scenarios of potting adhesives are increasing, and the requirements for potting adhesives are also getting higher and higher. As a typical representative of potting adhesives, the demand for polyurethane potting adhesives has also increased year by year.

[0003] Chinese Patent CN116656306B discloses a polyurethane potting adhesive, which includes an A component and a B component; the A component includes castor oil, a first polyether polyol, a second polyether polyol, a mixed auxiliary agent, and aluminum hydroxide; the B component includes polymeric MDI; the mixed auxiliary agent is a mixture composed of a wetting dispersant, a viscosity reducer, and an antifoaming agent. It solves the problem that the defoaming ability of the existing potting adhesives on the market is insufficient to completely eliminate bubbles, and even if the bubbles can be completely eliminated, an excessive amount of antifoaming agent needs to be added to achieve complete bubble elimination.

[0004] However, the potting adhesive in the above-mentioned prior art cannot well solve the heat dissipation problem of high-power electronic components, and its thermal conductivity still needs to be improved. Summary of the Invention

[0005] In order to solve the problems in the prior art, in the first aspect of the present invention, a high thermal conductivity polyurethane potting adhesive is provided, and its preparation raw materials include: an A component and a B component; the preparation raw materials of the A component include MDI, a first plasticizer, a first thermal conductivity filler, and a first dispersant; the preparation raw materials of the B component include a polyol, a second plasticizer, a second thermal conductivity filler, and an auxiliary agent; both the first thermal conductivity filler and the second thermal conductivity filler are a composition of BN nanosheets, spherical alumina, and diamond powder;

[0006] The average particle size of the BN nanosheets is larger than the average particle size of the spherical alumina; the average particle size of the spherical alumina is 2 - 12 μm; the spherical alumina at least includes a first spherical alumina and a second spherical alumina; the average particle size of the first spherical alumina is larger than the average particle size of the second spherical alumina.

[0007] In one embodiment, the average particle size of the BN nanosheets is 18 ± 2 μm.

[0008] The applicant creatively found that when the average particle size of BN nanosheets in the system is larger than that of spherical alumina, especially when the average particle size of BN nanosheets is 18 μm, the finally prepared polyurethane potting adhesive has good thermal conductivity and low viscosity. The possible reason is that when the average particle size of BN nanosheets in the system is too large, the sedimentation performance of the product decreases, and when the average particle size of BN nanosheets in the system is too small, it will cause the product to have high viscosity and reduced fluidity.

[0009] In one embodiment, the average particle size of the first spherical alumina is 12 μm.

[0010] In one embodiment, the average particle size of the second spherical alumina is 2 μm.

[0011] In one embodiment, the average particle size of the diamond powder is 12 μm.

[0012] The applicant found that the selection of thermal conductive fillers has a great influence on the dispersion effect. When irregular alumina or flaky alumina is used, the finally prepared polyurethane potting adhesive has high viscosity and poor thermal conductivity. The applicant creatively found that when the thermal conductive filler includes spherical alumina with different particle sizes used in combination, especially when the particle size of the spherical alumina is controlled to be a combination of 2 μm and 12 μm, it can ensure that the finally prepared polyurethane potting adhesive takes into account good stability, fluidity and thermal conductivity.

[0013] In one embodiment, the mass ratio of the first spherical alumina to the second spherical alumina is (20 - 46):(45 - 46).

[0014] In one embodiment, the mass ratio of the first spherical alumina to the second spherical alumina is 4:9.

[0015] In one embodiment, the total mass of the first plasticizer and MDI and the mass of the first thermal conductive filler have a ratio of 12:92.

[0016] In one embodiment, the total mass of the polyol and the second plasticizer and the mass of the second thermal conductive filler have a ratio of 8:91.

[0017] In one embodiment, the first plasticizer and the second plasticizer are both one or more of epoxy soybean oil, DOA, DOTP, DOP, TCP, and TCPP.

[0018] In one embodiment, the first plasticizer is a combination of epoxy soybean oil and DOA.

[0019] In one embodiment, the mass ratio of epoxy soybean oil to DOA is 1:3.

[0020] In one embodiment, the epoxy soybean oil is purchased from Tongxiang Chemical Industry.

[0021] In one embodiment, the second plasticizer is DOA, and the DOA is purchased from Kunshan Weifeng Chemical Industry.

[0022] In one embodiment, the additives include one or more of molecular sieve, defoamer, catalyst and second dispersant.

[0023] In one embodiment, the additives include molecular sieve, defoamer, catalyst and second dispersant.

[0024] In one embodiment, the molecular sieve is 5A molecular sieve, and the 5A molecular sieve is purchased from Luoyang Jianlong Micro-Nano New Materials Co., Ltd.

[0025] In one embodiment, the defoamer is selected from any one of silicone defoamers and non-silicone defoamers.

[0026] In one embodiment, the defoamer is a non-silicone defoamer, and the grade of the non-silicone defoamer is BYK-2735, which is purchased from BYK-Chemie.

[0027] In one embodiment, the catalyst is selected from any one of organotin catalysts and polyurethane delay catalysts.

[0028] In one embodiment, the catalyst is an organotin catalyst, and the grade of the organotin catalyst is MT101, which is purchased from Mingtai Chemical Industry.

[0029] In one embodiment, both the first dispersant and the second dispersant are BYK-9076, which are purchased from BYK-Chemie.

[0030] In one embodiment, the mass ratio of the mixture of the first plasticizer and the first thermal conductive filler to the first dispersant is 500:1.

[0031] In one embodiment, the mass ratio of the mixture of the polyol, the second plasticizer and the second thermal conductive filler to the second dispersant is 1000:3.

[0032] In one embodiment, the polyol includes one or more of castor oil, modified castor oil, modified soybean oil polyol, modified cashew shell oil polyol, polyether polyol, dipropylene glycol, 1,4-butanediol, ethylene glycol, 2-ethyl-1,3-hexanediol.

[0033] In one embodiment, the polyol includes one or two of castor oil and dipropylene glycol.

[0034] In one embodiment, the polyol is castor oil and dipropylene glycol.

[0035] In one embodiment, the mass ratio of the second plasticizer, castor oil, and dipropylene glycol is 2:9:1.

[0036] In one embodiment, the MDI includes any one of pure MDI, liquefied MDI, and polymeric MDI.

[0037] In one embodiment, the MDI is liquefied MDI, with the grade MDI-100L, purchased from Wanhua Chemical.

[0038] The second aspect of the present invention provides a method for preparing a highly thermally conductive polyurethane potting adhesive, which is characterized by at least including the following steps:

[0039] S1. Preparation of component A: After completely mixing and dispersing the first plasticizer, the first thermally conductive filler, and the first dispersant, add MDI, mix and discharge the material, and store it sealed to obtain component A;

[0040] S2. Preparation of component B: After uniformly mixing the polyol, the second plasticizer, the second thermally conductive filler, and the auxiliary agent, discharge the material and store it sealed to obtain component B.

[0041] In one embodiment, the preparation of component A includes the following steps: predisperse the first plasticizer and BN nanosheets, then enter a homogenizing device and disperse for 30 - 60 min, add spherical alumina, diamond powder, and the first dispersant, disperse for 30 min, heat up to 110 - 130 °C, turn on the vacuum device to remove water for 120 min, test the moisture content of the material, when the moisture content is lower than 150 ppm, cool down to 60 °C, add MDI, mix for 30 min, then discharge the material and store it sealed to obtain component A.

[0042] In one embodiment, the vacuum degree of the vacuum device is set to 0.1 MPa.

[0043] In one embodiment, the preparation of component B includes the following steps: predisperse the polyol, the second plasticizer, and BN nanosheets, then enter a homogenizing device and disperse for 30 - 60 min, add spherical alumina, diamond powder, and the second dispersant, disperse for 30 min, heat up to 110 - 130 °C, turn on the vacuum device to remove water for 120 min, test the moisture content of the material, when the moisture content is lower than 150 ppm, cool down to 75 - 85 °C, add molecular sieve, defoamer, and catalyst, mix and disperse for 30 min, and turn on the vacuum at the same time; after mixing evenly, discharge the material and store it sealed to obtain component B.

[0044] In one embodiment, the time for predispersion is 10 min.

[0045] Beneficial effects

[0046] 1. Based on the system of the present invention, spherical alumina with different particle sizes is used in combination. Especially when the average particle sizes of the spherical alumina are controlled to be a combination of 2 μm and 12 μm and the mass ratio of the two spherical aluminas is controlled, it can ensure that the finally prepared polyurethane potting adhesive has good stability, fluidity and heat conduction effect.

[0047] 2. Based on the system of the present invention, when the particle size of the BN nanosheets in the heat-conducting filler is controlled to be larger than that of the spherical alumina, especially when the average particle size of the BN nanosheets is 16 - 18 μm, the finally prepared polyurethane potting adhesive has good heat conduction effect and low viscosity.

[0048] 3. The present invention can obtain a polyurethane potting adhesive with high thermal conductivity by selecting a specific combination of heat-conducting fillers, strictly controlling the dosage ratio of each component in the heat-conducting filler and the dosage of the heat-conducting filler.

[0049] 4. The polyurethane potting adhesive prepared by the present invention has low viscosity and good flowability, is suitable for potting requirements, and has high thermal conductivity, which can better solve the heat dissipation problem of electronic components and improve the service life of client products.

[0050] 5. The preparation method of the polyurethane potting adhesive provided by the present invention can be applied to industrial production and has higher practical value. Specific Embodiments

[0051] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. The experimental methods without specific conditions noted in the embodiments are carried out according to conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments without the manufacturer noted are all conventional products that can be obtained through commercial purchase.

[0052] Examples 1 - 4, Comparative Examples 1 - 4

[0053] In Examples 1 - 4 and Comparative Examples 1 - 4 of the present invention, a high thermal conductivity polyurethane potting adhesive is provided in the first aspect. The preparation raw materials are shown in Tables 1 and 2 respectively according to weight parts.

[0054] In Examples 1 - 4 and Comparative Examples 1 - 4 of the present invention, a preparation method of a high thermal conductivity polyurethane potting adhesive is provided in the second aspect, including the following steps:

[0055] Preparation of Component A: The first plasticizer and BN nanosheets were pre-dispersed for 10 min, then entered the homogenization equipment for dispersion for 40 min. After that, spherical alumina, diamond powder and the first dispersant were added, and after dispersion for 30 min, the temperature was raised to 120 °C and the vacuum equipment was turned on to remove water for 120 min. Then the moisture of the material was tested. When the moisture was lower than 150 ppm, the temperature was lowered to 60 °C and MDI was added. After mixing for 30 min, the product was discharged and stored in a sealed manner, thus obtaining Component A.

[0056] The preparation of Component B includes the following steps: Polyol, the second plasticizer and BN nanosheets were pre-dispersed for 10 min, then entered the homogenization equipment for dispersion for 40 min. After that, spherical alumina, diamond powder and the second dispersant were added, and after dispersion for 30 min, the temperature was raised to 120 °C and the vacuum equipment was turned on to remove water for 120 min. Then the moisture of the material was tested. When the moisture was lower than 150 ppm, the temperature was lowered to 80 °C and molecular sieve, defoamer and catalyst were added, and they were mixed and dispersed for 30 min while the vacuum was turned on. After mixing evenly, the product was discharged and stored in a sealed manner, thus obtaining Component B.

[0057] Performance Test

[0058] 1. Viscosity Test: The viscosities of Component A and Component B prepared in Examples 1-4 and Comparative Examples 1-4 were tested using a rheometer (NETZSCH, Lab+). The test results are shown in Tables 1 and 2.

[0059] 2. Thermal Conductivity Test: The samples prepared in Examples 1-4 and Comparative Examples 1-4 were made into thin slices with a thickness of 2 mm, and then cut into dimensions of 20 mm * 20 mm * 2 mm, and tested using a thermal conductivity tester (Hot disk TPS3500). The test results are shown in Table 3, where " / " in the table represents that the relevant test could not be carried out.

[0060] Method for Preparing Thin Slices: Component A and Component B were weighed according to a weight ratio of 104:100 using an electronic balance, stirred evenly with a glass rod, and then placed in a vacuum desiccator for vacuum defoaming treatment. After no obvious bubbles were generated on the surface of the glue, the vacuum desiccator was closed, and the glue was poured into a mold with a thickness of 2 mm and cured at room temperature for 72 h, and the 2-mm-thick thin slices were made.

[0061] Table 1

[0062]

[0063] Table 2

[0064]

[0065] Table 3

[0066]

Claims

1. A high thermal conductivity polyurethane potting adhesive, characterized in that, Its preparation raw materials include: Component A and Component B; the preparation raw materials of Component A include MDI, a first plasticizer, a first heat-conducting filler, and a first dispersant; the preparation raw materials of Component B include a polyol, a second plasticizer, a second heat-conducting filler, and an auxiliary agent; both the first heat-conducting filler and the second heat-conducting filler are compositions including BN nanosheets, spherical alumina, and diamond powder; The average particle size of the BN nanosheets is 18±2μm; the spherical alumina at least includes first spherical alumina and second spherical alumina; the average particle size of the first spherical alumina is 12μm; the average particle size of the second spherical alumina is 2μm; the average particle size of the diamond powder is 12μm.

2. The high thermal conductivity polyurethane potting adhesive according to claim 1, wherein The mass ratio of the first spherical alumina to the second spherical alumina is (20-46):(45-46).

3. The high thermal conductivity polyurethane potting adhesive according to claim 1, characterized in that Both the first plasticizer and the second plasticizer are one or more of epoxy soybean oil, DOA, DOTP, DOP, TCP, and TCPP.

4. The high thermal conductivity polyurethane potting adhesive according to claim 1, wherein The auxiliary agent includes one or more of molecular sieve, defoamer, catalyst, and second dispersant.

5. The high thermal conductivity polyurethane potting adhesive according to claim 1, characterized in that, The polyol includes one or more of castor oil, modified castor oil, modified soybean oil polyol, modified cashew shell oil polyol, polyether polyol, dipropylene glycol, 1,4-butanediol, ethylene glycol, and 2-ethyl-1,3-hexanediol.

6. A preparation method of the high thermal conductivity polyurethane potting adhesive according to any one of claims 1-5, characterized in that, It at least includes the following steps: S1. Preparation of Component A: After the first plasticizer, the first heat-conducting filler, and the first dispersant are mixed and dispersed completely, MDI is added, mixed and discharged, and stored sealed to obtain Component A; S2. Preparation of Component B: The polyol, the second plasticizer, the second heat-conducting filler, and the auxiliary agent are mixed evenly and then discharged, and stored sealed to obtain Component B.

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