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CN-121975154-A - Heat-conducting polyimide powder and preparation method thereof

CN121975154ACN 121975154 ACN121975154 ACN 121975154ACN-121975154-A

Abstract

The application belongs to the technical field of polyimide materials, and discloses a heat-conducting polyimide powder and a preparation method thereof, wherein the preparation method comprises the following preparation steps of carrying out hydrophilic modification on a flaky heat-conducting filler through polyethylene glycol to obtain a hydrophilic filler containing a polyethylene glycol coating layer, and then mixing the hydrophilic filler with a phase substance, heating and stirring to obtain a phase solution, wherein the phase substance comprises at least one of n-eicosane, microcrystalline wax and dimethyl silicone oil; the preparation method comprises the steps of carrying out hydrophobic modification on spherical heat conduction filler through epoxy silane to obtain epoxy silane coated hydrophobic filler, carrying out melt mixing on the hydrophobic filler and polyimide to obtain melt, stirring the solution, adding the solution into the melt, heating, stirring, atomizing and granulating to obtain heat conduction polyimide powder. The heat conduction polyimide powder prepared by the method can effectively improve the heat conduction effect.

Inventors

  • CHEN JUN
  • CHEN WEIYI
  • LI LUN
  • LI YU
  • SHI ZE
  • LAI LIN
  • HUANG XIAOBIN
  • WANG ZHEN

Assignees

  • 成都信达高分子材料有限公司

Dates

Publication Date
20260505
Application Date
20260408

Claims (9)

  1. 1. The preparation method of the heat-conducting polyimide powder is characterized by comprising the following preparation steps: S1, carrying out hydrophilic modification on a platy heat-conducting filler through polyethylene glycol to obtain a hydrophilic filler containing a polyethylene glycol coating layer, and then mixing the hydrophilic filler with a phase substance, heating and stirring to obtain a phase solution, wherein the phase substance comprises at least one of n-eicosane, microcrystalline wax and dimethyl silicone oil; S2, carrying out hydrophobic modification on the spherical heat-conducting filler through epoxy silane to obtain an epoxy silane coated hydrophobic filler; And S3, carrying out melt mixing on the hydrophobic filler and polyimide to obtain a melt, stirring the solution, adding the solution into the melt, heating, stirring, atomizing and granulating to obtain the heat-conducting polyimide powder.
  2. 2. The method for preparing a thermally conductive polyimide powder according to claim 1, wherein the thermally conductive flake filler in step S1 includes at least one of flake boron nitride, flake aluminum nitride, and flake graphene oxide, and the polyethylene glycol is a hydroxyl polyethylene glycol mercapto group and/or a dimercapto polyethylene glycol, and step S1 includes: S1.1, dispersing a flaky heat-conducting filler in a strong acid solution, carrying out ultrasonic auxiliary treatment at 55-65 ℃ for 4-6 hours, pouring the solution into ice water, quenching, centrifuging, filtering, and washing the solution to be neutral to obtain a pretreated flaky filler, wherein the mass ratio of the flaky heat-conducting filler to the strong acid solution is 1:20-30, and the strong acid solution consists of 65-68% concentrated nitric acid and 95-98% concentrated sulfuric acid according to a volume ratio of 1:3; s1.2, adding the pretreated flaky filler into Tris-HCl buffer solution with the concentration of the polyamine hydrochloride of 0.15-0.25wt% and the pH=8.5, stirring at room temperature for reacting for 20-24 hours, filtering and washing to obtain polydopamine coated filler, wherein the mass ratio of the pretreated flaky filler to the Tris-HCl buffer solution is 1 (15-25); S1.3, adding the polydopamine coated filler into a PBS buffer solution with the polyethylene glycol concentration of 1-2wt% and the pH value of 7.4, stirring and reacting for 10-14 hours at the temperature of 40-50 ℃, filtering, washing and drying to obtain a hydrophilic filler, wherein the mass ratio of the polydopamine coated filler to the PBS buffer solution is 1 (10-20); S1.4, mixing the hydrophilic filler with the phase substance, heating to 100-120 ℃, and uniformly stirring to obtain a phase solution, wherein the mass ratio of the hydrophilic filler to the phase substance is 1 (3-6).
  3. 3. The method for preparing a thermally conductive polyimide powder according to claim 1, wherein the spherical thermally conductive filler in step S2 comprises at least one of spherical alumina, spherical zinc oxide, and spherical silica, and the epoxysilane is 3-glycidoxypropyl trimethoxysilane and/or 3-glycidoxypropyl methyldiethoxysilane.
  4. 4. The method for preparing a thermally conductive polyimide powder according to claim 1, wherein step S2 comprises: S2.1, pretreating the spherical heat-conducting filler in an oxygen plasma machine with power of 100-200W and oxygen flow of 45-55 sccm for 10-20 min to obtain pretreated spherical filler; S2.2, adding the pretreated spherical filler into anhydrous toluene with the concentration of 1-2 vol% of perfluorosilane, stirring and reacting for 5-7 hours at 75-85 ℃ in an inert atmosphere, filtering, alternately washing for 3-5 times by toluene and ethanol, and drying to obtain the perfluorofiller, wherein the mass ratio of the pretreated spherical filler to the anhydrous toluene is 1 (10-20), and the perfluorosilane is 1H, 2H-perfluorooctyl triethoxysilane and/or heptadecafluorodecyl trimethoxysilane; s2.3, adding the perfluorinated filler into a mixed solution with the epoxy silane concentration of 1-2 vol%, regulating the pH to 4-5 by using an acidic reagent, stirring and reacting for 3-5 hours at 55-65 ℃, filtering, washing by ethanol, and drying to obtain the hydrophobic filler, wherein the acidic reagent comprises at least one of acetic acid, citric acid and hydrochloric acid.
  5. 5. The method for preparing a thermally conductive polyimide powder according to claim 1, wherein step S3 comprises: s3.1, adding a phase regulator into the phase solution, stirring for 20-30 min at 100-120 ℃, and preserving heat to obtain a regulated phase solution, wherein the addition amount of the phase regulator is 0.5-3.0wt% of the mass of the phase solution; S3.2, after mixing the hydrophobic filler and polyimide, heating to 120-150 ℃, stirring for 20-30 min, and preserving heat to obtain a melt, wherein the mass ratio of the hydrophobic filler to the polyimide is (0.10-0.25): 1; S3.3, stirring and adding the regulated phase solution into the molten solution, stirring for 10-20 min, heating to 220-250 ℃ at a heating rate of 5-10 ℃ per min, and stirring for 1-2 h to obtain a mixed solution, wherein the mass ratio of the regulated phase solution to the molten solution is (0.2-0.4): 1; And S3.4, carrying out atomization granulation on the mixed solution in an inert atmosphere in an atomization tower at 220-250 ℃ to obtain the heat-conducting polyimide powder.
  6. 6. The method for producing a heat conductive polyimide powder according to claim 5, wherein when the phase substance is n-dodecane, microcrystalline wax, the phase modifier comprises at least one of glycerol monostearate, polyethylene glycol distearate, and erucamide; when the phase material is dimethicone, the phase modifier comprises at least one of N- (trimethylsilyl) acetamide, bis (trimethylsilyl) acetamide, PEG-10 polydimethylsiloxane.
  7. 7. The method according to claim 1 or 5, wherein the viscosity of the melt is adjusted to a predetermined viscosity range when the phase solution is added to the melt with stirring.
  8. 8. The method for preparing a heat conductive polyimide powder according to claim 7, wherein the specific step of adjusting the viscosity of the melt to a predetermined viscosity range is as follows: detecting whether the viscosity of the melt reaches a preset range by using a viscometer; If yes, adding a phase solution; if not, adding a viscosity adjusting substance, and repeatedly using a viscometer to detect the viscosity of the melt; the viscosity regulating substance mainly comprises octamethyl cyclotetrasiloxane for reducing viscosity and hydrogenated castor oil for increasing viscosity.
  9. 9. A thermally conductive polyimide powder, characterized in that it is produced by a process for producing a thermally conductive polyimide powder according to any one of claims 1 to 8.

Description

Heat-conducting polyimide powder and preparation method thereof Technical Field The application relates to the technical field of polyimide materials, in particular to heat-conducting polyimide powder and a preparation method thereof. Background Polyimide powder coatings, which are representative of high-performance polymer coatings, exhibit excellent high temperature resistance (long-term resistance to 250 ℃ or more), excellent electrical insulation strength, excellent mechanical toughness, and good chemical stability by virtue of their molecular backbones composed of rigid aromatic heterocycles and imide rings, and are in an irreplaceable position in high-end fields such as power electronics, aerospace, and new energy automobiles. The method is particularly applied to the key scenes of insulating coating of motor electromagnetic wires, protection of high-frequency transformer coils, surface coating of a flexible circuit board, encapsulation of high-temperature sensors and the like, and provides reliable insulation and environmental protection for precision devices. However, the material has obvious heat dissipation defect that heat is accumulated in the coating and is difficult to diffuse because of extremely low intrinsic heat conductivity coefficient and multiple phonon scattering centers such as particle fusion interfaces, microscopic pores and the like exist in the coating. The heat accumulation effect can cause the continuous rise of local temperature, accelerate the thermo-oxidative aging and chemical degradation of a high molecular chain, promote the gradual decline of insulation performance and the decline of mechanical strength, and finally obviously shorten the service life of a coating under the coupling action of thermo-electric-mechanical multiple stresses, thereby becoming a key bottleneck for restricting the long-term reliable application of the coating in a high-efficiency heat dissipation scene. Disclosure of Invention The invention aims to solve the technical problem of reduced service life of a polyimide coating caused by poor heat conduction effect of polyimide powder. In order to solve the technical problems, the invention provides a preparation method of heat-conducting polyimide powder, which comprises the following preparation steps: S1, carrying out hydrophilic modification on a platy heat-conducting filler through polyethylene glycol to obtain a hydrophilic filler containing a polyethylene glycol coating layer, and then mixing the hydrophilic filler with a phase substance, heating and stirring to obtain a phase solution, wherein the phase substance comprises at least one of n-eicosane, microcrystalline wax and dimethyl silicone oil; S2, carrying out hydrophobic modification on the spherical heat-conducting filler through epoxy silane to obtain an epoxy silane coated hydrophobic filler; And S3, carrying out melt mixing on the hydrophobic filler and polyimide to obtain a melt, stirring the solution, adding the solution into the melt, heating, stirring, atomizing and granulating to obtain the heat-conducting polyimide powder. In some embodiments, the platy heat-conducting filler in step S1 includes at least one of platy boron nitride, platy aluminum nitride, and platy graphene oxide, and the polyethylene glycol is a hydroxyl polyethylene glycol mercapto group and/or a dimercapto polyethylene glycol, and step S1 includes: S1.1, dispersing a flaky heat-conducting filler in a strong acid solution, carrying out ultrasonic auxiliary treatment at 55-65 ℃ for 4-6 hours, pouring the solution into ice water, quenching, centrifuging, filtering, and washing the solution to be neutral to obtain a pretreated flaky filler, wherein the mass ratio of the flaky heat-conducting filler to the strong acid solution is 1:20-30, and the strong acid solution consists of 65-68% concentrated nitric acid and 95-98% concentrated sulfuric acid according to a volume ratio of 1:3; s1.2, adding the pretreated flaky filler into Tris-HCl buffer solution with the concentration of the polyamine hydrochloride of 0.15-0.25wt% and the pH=8.5, stirring at room temperature for reacting for 20-24 hours, filtering and washing to obtain polydopamine coated filler, wherein the mass ratio of the pretreated flaky filler to the Tris-HCl buffer solution is 1 (15-25); S1.3, adding the polydopamine coated filler into a PBS buffer solution with the polyethylene glycol concentration of 1-2wt% and the pH value of 7.4, stirring and reacting for 10-14 hours at the temperature of 40-50 ℃, filtering, washing and drying to obtain a hydrophilic filler, wherein the mass ratio of the polydopamine coated filler to the PBS buffer solution is 1 (10-20); S1.4, mixing the hydrophilic filler with the phase substance, heating to 100-120 ℃, and uniformly stirring to obtain a phase solution, wherein the mass ratio of the hydrophilic filler to the phase substance is 1 (3-6). In some embodiments, the spherical thermally conductive filler in step S2 compr