Core-shell structure modified boron nitride and preparation method thereof

文档序号：1871549 发布日期：2021-11-23 浏览：17次中文

阅读说明：本技术 一种核壳结构改性氮化硼及其制备方法 (Core-shell structure modified boron nitride and preparation method thereof ) 是由马峰岭金石磊李小慧侯李明马海龙于 2021-08-27 设计创作，主要内容包括：本发明涉及高导热复合材料领域,尤其是涉及一种核壳结构改性氮化硼及其制备方法。本发明将氮化硼表面经碱溶液和硅烷偶联剂处理后得到表面初步改性的氮化硼,随后将聚硅氮烷包覆在表面处理过后的氮化硼上,聚硅氮烷经反应接枝在氮化硼表面形成氮化硼的聚硅氮烷包覆体,将包覆体置于有水气氛的环境下进行缩合反应,最终得到表面壳层具有致密氧化硅的改性氮化硼。采用该方法制备的改性氮化硼可以明显改善其分散特性,其结构强度和导热特性也大大提高。(The invention relates to the field of high-thermal-conductivity composite materials, in particular to core-shell structure modified boron nitride and a preparation method thereof. The surface of boron nitride is treated by an alkali solution and a silane coupling agent to obtain the boron nitride with the surface preliminarily modified, then polysilazane is coated on the boron nitride with the surface treated, the polysilazane is grafted on the surface of the boron nitride through reaction to form a polysilazane coating of the boron nitride, and the coating is placed in an environment with water atmosphere for condensation reaction to finally obtain the modified boron nitride with a compact silicon oxide on the surface shell. The modified boron nitride prepared by the method can obviously improve the dispersion characteristic, and the structural strength and the heat conduction characteristic are also greatly improved.)

1. A core-shell structure modified boron nitride and a preparation method thereof are characterized by comprising the following steps:

(1) grafting and modifying boron nitride by a polysilazane polymer to obtain modified boron nitride with polysilazane grafted on the surface;

(2) in the presence of water atmosphere, the polysilazane on the surface of the modified boron nitride is subjected to hydrolytic condensation reaction to form dense SiO on the surface of BN₂And obtaining the core-shell structure modified boron nitride by using a shell layer.

2. The core-shell structure modified boron nitride and the preparation method thereof according to claim 1, wherein in the step (1), the polysilazane polymer is selected from a polysilazane or a mixture of two or more polysilazanes; preference is given to perhydropolysilazanes.

3. The core-shell structure modified boron nitride and the preparation method thereof according to claim 2, wherein the polysilazane polymer is a polymer with a molecular main chain of a Si-N structure, and the general structural formula is shown in the following formula (I):

wherein R1 is a hydrogen atom or an organic group, R2 is a hydrogen atom or an organic group; n is the degree of polymerization and is an integer;

the number average molecular weight of the polysilazane polymer is preferably 150-55000.

4. The core-shell structure modified boron nitride and the preparation method thereof according to claim 1, wherein in the step (1), the method for graft modification of boron nitride by polysilazane comprises wet method, dry method or gas phase method.

5. The core-shell structure modified boron nitride and the preparation method thereof according to claim 4, wherein the wet method of graft modification of boron nitride by polysilazane polymer is as follows: dissolving the polysilazane polymer in a solvent, then adding boron nitride into the dissolved solution for grafting reaction, and removing the solvent after the reaction is finished to obtain the modified boron nitride with the polysilazane grafted on the surface.

6. The core-shell structure modified boron nitride and the preparation method thereof according to claim 5, wherein the solvent removal method is centrifugal separation.

7. The core-shell structure modified boron nitride and the preparation method thereof according to claim 1, wherein in the step (1), the reaction temperature in the grafting reaction process is normal temperature to 300 ℃.

8. The core-shell structure modified boron nitride and the preparation method thereof according to claim 1, wherein the boron nitride is subjected to surface pre-modification treatment before being grafted with polysilazane, and the surface treatment comprises alkali solution treatment or silane coupling agent treatment;

the alkali liquor comprises one or more of sodium hydroxide solution, potassium hydroxide solution, ammonia water and hydrogen peroxide; the silane coupling agent is selected from one or more of vinyl silane coupling agent, acrylic silane coupling agent, amino silane coupling agent and epoxy silane coupling agent.

9. The core-shell structure modified boron nitride and the preparation method thereof according to claim 1, wherein in the step (2), the reaction temperature in the hydrolysis condensation reaction process is normal temperature-300 ℃.

10. A core-shell structure modified boron nitride characterized by being prepared by the method of any one of claims 1 to 9, having a BN surface with dense SiO₂And (4) shell layer.

Technical Field

The invention relates to the field of high-thermal-conductivity composite materials, in particular to core-shell structure modified boron nitride and a preparation method thereof.

Background

The polymer-based heat-conducting composite material is widely applied to the field of electronic materials due to excellent performance and lower cost. With the rapid development of the internet of things and the 5G technology, electronic components become more miniaturized and integrated, which also puts higher requirements on the heat conductivity of the components. The polymer-based heat conductive material is generally composed of a polymer matrix and heat conductive powder, and the heat conductive powder generally includes ceramic, carbon, metal and the like. Boron nitride is a ceramic filler. The crystal structure of the boron nitride can be roughly divided into hexagonal boron nitride, cubic boron nitride, rhombohedral boron nitride and wurtzite nitride, and the application of the hexagonal boron nitride and the cubic boron nitride is mainly used in the market. Boron Nitride (BN) is widely used as a filler for raw materials of electronic devices with excellent thermal conductivity and insulation properties.

BN is a hexagonal crystal structure similar to graphene and is formed by stacking multiple layers, and the layers are combined through weak van der Waals interaction, so that the BN is in a lamellar shape and is easily subjected to shear delamination and brittle fracture in a composite material system, so that the BN is dispersed in the composite system in a finer lamellar shape, and the viscosity of the system is greatly increased, so that the filling usage amount of the BN is greatly reduced. The lamellar BN still has large specific surface area and is easy to float near the surface of a composite material system, so that the solubility and the dispersibility of the BN are poor, and the heat-conducting property of the material is further influenced.

Disclosure of Invention

The conventional BN powder has a lamellar structure, the lamellar BN is high in brittleness, poor in interlayer bonding force, the powder structure state is easily damaged, and the powder easily floats on the surface of a dispersing agent in the dispersing agent and is not beneficial to the dispersion of the BN, so that the thermal conductivity and the stability of the material are obviously influenced. In order to improve the dispersibility of BN in a dispersing agent and improve the stability of lamellar BN in a composite system, the invention aims to provide core-shell structure modified boron nitride and a preparation method thereof. By improving the dispersibility and stability of BN in the dispersing agent, the heat-conducting property of the material is obviously improved, and the hardness and the strength of the material are both improved to a great extent.

According to the invention, BN is grafted and modified by polysilazane, and the polysilazane can form compact silicon oxide ceramic at a lower temperature, so that compact SiO can be formed on the surface of BN₂The core-shell structure of the coating layer can greatly improve the interlaminar anti-damage strength and the dispersion characteristic of BN, and the heat-conducting property of the BN composite material system can be greatly improved.

The purpose of the invention can be realized by the following technical scheme:

the first purpose of the invention is to provide a core-shell structure modified boron nitride and a preparation method thereof, wherein the preparation method comprises the following steps:

(1) grafting and modifying boron nitride by a polysilazane polymer to obtain modified boron nitride with polysilazane grafted on the surface;

In one embodiment of the present invention, in step (1), the polysilazane polymer is selected from one polysilazane or a mixture of two or more polysilazanes; perhydropolysilazanes are preferred because of their low curing temperature and the resulting cured product after curing is dense.

In one embodiment of the present invention, the polysilazane polymer is a polymer having a molecular main chain with a Si — N structure, and the general structural formula is shown in the following formula (I):

wherein R1 is a hydrogen atom or an organic group, R2 is a hydrogen atom or an organic group; n is the degree of polymerization and is an integer;

the number average molecular weight of the polysilazane polymer is preferably 150-55000.

In one embodiment of the present invention, the method for graft-modifying boron nitride with polysilazane in step (1) includes a wet method, a dry method or a gas phase method.

In one embodiment of the invention, the wet method for graft modification of boron nitride by polysilazane polymer is: dissolving a polysilazane polymer in a solvent, then adding boron nitride into the dissolved solution for grafting reaction, and removing the solvent after the reaction is finished to obtain modified boron nitride with the surface grafted with polysilazane;

in one embodiment of the invention, the solvent removal means is centrifugation.

In one embodiment of the present invention, in step (1), the solvent includes, but is not limited to, hydrocarbons, halogenated hydrocarbons, ethers; the hydrocarbons include, but are not limited to, aliphatic hydrocarbons, alicyclic hydrocarbons, aromatic hydrocarbons; the ethers are selected from one or more of aliphatic ethers and alicyclic ethers.

Further, hydrocarbons include, but are not limited to, pentane, hexane, methylpentane, heptane, octane, cyclopentane, cyclohexane, toluene, xylene; halogenated hydrocarbons include, but are not limited to, dichloromethane, chloroform, carbon tetrachloride, bromoform, 1, 2-dichloroethane, 1-dichloroethane, trichloroethane, tetrachloroethane; ethers include, but are not limited to, diethyl ether, isopropyl ether, tetrahydropyran.

In one embodiment of the invention, in the step (1), the reaction temperature in the grafting reaction process is normal temperature to 300 ℃, and the reaction time is adjusted according to different temperatures.

In one embodiment of the invention, the boron nitride may be subjected to a surface pre-modification treatment before the polysilazane is grafted, the surface treatment including an alkali treatment or a silane coupling agent treatment;

In one embodiment of the invention, in the step (2), the reaction temperature in the hydrolysis condensation reaction process is normal temperature to 300 ℃, and the reaction time is adjusted according to different temperatures.

In one embodiment of the invention, BN can be subjected to surface modification firstly, the BN is placed in NaOH solution to react to obtain modified BN with the surface rich in-OH groups, and the grafting amount of polysilazane can be effectively improved by introducing more-OH groups into the surface of the BN, so that the shell structure is more compact and complete.

Furthermore, the modified BN can be subjected to secondary surface modification by adopting a silane coupling agent, and the silane coupling agent can be grafted on the surface of the BN and further introduces more-OH groups; by adopting BN enriched with-OH groups to carry out polysilazane grafting reaction treatment, thicker and denser SiO can be obtained₂And (4) shell layer.

The hydrolysis condensation reaction of polysilazane of the invention is a slow process, as shown in formula (II) and formula (III), its reaction mechanism is mainly through hydrolysis and deamidation dehydrogenation reaction to get Si-O structure, and wrap around BN closely.

The second purpose of the invention is to provide core-shell structure modified boron nitride, which is prepared by the method, and compact SiO is obtained on the BN surface₂And (4) shell layer.

In one embodiment of the invention, the core-shell structure modified boron nitride can be used in the field of high thermal conductivity composite materials, is suitable for the field of electronic information science, and is particularly a matrix filler of electronic components.

Compared with the prior art, the invention has the following advantages:

(1) the original BN surface has few active functional groups, which is not beneficial to the dispersion of the original BN in a dispersing agent, and the surface of the BN can be grafted with more active hydroxyl groups by the reaction of the BN in NaOH solution and the further surface treatment modification of the silane coupling agent, so that the surface modified BN can be better interacted with polysilazane to form a more compact shell layer silicon oxide structure.

(2) Reacting the hydroxyl group on the surface of the modified BN with polysilazane (action mechanism) to obtain polysilazane-coated BN; the uniformly dispersed polysilazane-coated core-shell structure BN is cured at room temperature or under the condition of heating or a catalyst, so that the polysilazane undergoes a hydrolytic oxidative condensation reaction to form a compact silicon oxide cross-linked body, and finally spherical BN powder is obtained, can be effectively dispersed in an organic solvent, greatly improves the hardness and strength of the material, and further improves the heat conductivity of the modified boron nitride filled composite material.

Detailed Description

The invention provides a core-shell structure modified boron nitride and a preparation method thereof, wherein the preparation method comprises the following steps:

(1) grafting and modifying boron nitride by a polysilazane polymer to obtain modified boron nitride with polysilazane grafted on the surface;

wherein R1 is a hydrogen atom or an organic group, R2 is a hydrogen atom or an organic group; n is the degree of polymerization and is an integer;

the number average molecular weight of the polysilazane polymer is preferably 150-55000.

In one embodiment of the present invention, the method for graft-modifying boron nitride with polysilazane in step (1) includes a wet method, a dry method or a gas phase method.

in one embodiment of the invention, the solvent removal means is centrifugation.

The core-shell structure modified boron nitride obtained by the method comprises BN, and dense SiO is arranged on the surface of the BN₂And (4) shell layer.

The present invention will be described in detail with reference to specific examples.

Those whose specific conditions are not specified in the examples are carried out according to conventional conditions or conditions recommended by the manufacturer; the reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.

Example 1

The embodiment provides core-shell structure modified boron nitride and a preparation method thereof.

Firstly, the methodAdding perhydropolysilazane into a toluene solvent to prepare a solution with the perhydropolysilazane content of 2 percent (mass fraction), then adding 10 mass percent of hexagonal boron nitride (h-BN) powder of the polysilazane solution, heating to 60 ℃ under the condition of ultrasonic dispersion for pre-reaction for 2 hours, removing the toluene solvent by adopting a centrifugal separation mode after the reaction is finished, then putting the BN powder into a drying oven for drying treatment at 120 ℃ for 1 hour, reducing the temperature to 60 ℃ after the powder is dried, keeping for 8 hours for full curing reaction, and obtaining SiO after the reaction is finished₂BN-coated core-shell structure modified powder.

As shown in Table 1, the shell structure thickness of the core-shell structure-modified boron nitride obtained in example 1 was 120 nm.

The modified epoxy resin composite material is filled with modified boron nitride, the filling amount of the boron nitride is 20 mass percent of the epoxy resin, the modified epoxy resin is cured, the heat conductivity is tested, and the heat conductivity coefficient at 50 ℃ is measured to be 0.62W/(m.K).

Example 2

The embodiment provides core-shell structure modified boron nitride and a preparation method thereof.

Dispersing 10 mass percent of BN in 0.5mol/L aqueous solution of NaOH, heating to 70 ℃ for 4 hours under the condition of ultrasonic dispersion, washing for 3 times by deionized water after centrifugal separation, drying in a drying box after washing to obtain a BN modified material, adding the modified BN into a toluene solution of 2 percent perhydropolysilazane, heating to 60 ℃ for pre-reaction for 2 hours under the condition of ultrasonic dispersion, removing a toluene solvent by adopting a centrifugal separation mode after the reaction is finished, then putting BN powder into the drying box for drying treatment for 1 hour at 120 ℃, reducing the temperature to 60 ℃ after the powder is dried, keeping for 8 hours for full curing reaction, and obtaining SiO after the reaction is finished₂BN-coated core-shell structure modified powder.

As shown in Table 1, the shell structure thickness of the core-shell structure-modified boron nitride obtained in example 2 was 860 nm.

Example 3

The embodiment provides core-shell structure modified boron nitride and a preparation method thereof.

Dispersing 10 mass percent of BN into 0.5mol/L aqueous solution of NaOH, heating to 70 ℃ for reaction for 4 hours under the condition of ultrasonic dispersion, adding the modified BN into aqueous solution of ethanol containing 2 percent of silane coupling agent KH570 after centrifugal separation, reacting for 3 hours under the condition of 60 ℃, centrifugally separating the modified BN after the reaction is finished, drying in a drying box to obtain a BN modified material, adding the modified BN into 2 percent of toluene solution of perhydropolysilazane, heating to 60 ℃ for pre-reaction for 2 hours under the condition of ultrasonic dispersion, removing the toluene solvent by adopting a centrifugal separation mode after the reaction is finished, then putting the BN powder into a drying box, drying for 1 hour at 120 ℃, reducing the temperature to 60 ℃ after the powder is dried, keeping for 8 hours for full curing reaction, and obtaining SiO after the reaction is finished₂BN-coated core-shell structure modified powder.

As shown in Table 1, the shell-layer structure thickness of the core-shell-structure-modified boron nitride obtained in example 3 was 1.4. mu.m.

Example 4

The embodiment provides core-shell structure modified boron nitride and a preparation method thereof.

Dispersing 10 mass percent of BN into 0.5mol/L aqueous solution of NaOH, heating to 70 ℃ for reaction for 4 hours under the condition of ultrasonic dispersion, adding the modified BN into aqueous solution of ethanol containing 2 percent of silane coupling agent KH570 after centrifugal separation, reacting for 3 hours under the condition of 60 ℃, centrifugally separating the modified BN after the reaction is finished, placing the modified BN in a drying box for drying to obtain a BN modified material, adding the modified BN into 2 percent toluene solution of dimethyl polysilazane, heating to 60 ℃ for pre-reaction for 2 hours under the condition of ultrasonic dispersion, removing the toluene solvent by adopting a centrifugal separation mode after the reaction is finished, then placing BN powder into a drying box for drying at 120 ℃ in an ovenDrying for 1h, reducing the temperature to 60 ℃ after the powder is dried, keeping the temperature for 8h for full curing reaction, and obtaining SiO after the reaction is finished₂BN-coated core-shell structure modified powder.

As shown in Table 1, the shell structure thickness of the core-shell structure-modified boron nitride obtained in example 4 was 1.1. mu.m.

Comparative example 1

The unmodified boron nitride is adopted to fill the modified epoxy resin composite material, the filling amount of the boron nitride is 20 mass percent of the epoxy resin, the modified epoxy resin is cured, the heat conductivity is tested, and the heat conductivity coefficient at 50 ℃ is measured to be 0.58W/(m.K).

The structural characterization of the modified powder in the examples shows that, as shown in the following table, the modified BN in the examples has a thicker shell layer along with the optimization of the surface treatment mode, and the perhydropolysilazane has the best modification effect and a relatively denser shell layer structure.

Table 1 examples 1-4 and comparative examples shell structure thickness table

The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.

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Core-shell structure modified boron nitride and preparation method thereof

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