CN112210262A

CN112210262A - Heat-conducting coating and preparation method thereof

Info

Publication number: CN112210262A
Application number: CN202011093355.1A
Authority: CN
Inventors: 于杰; 慕永彪; 梁静冰
Original assignee: Songshan Lake Materials Laboratory
Current assignee: Songshan Lake Materials Laboratory
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2021-01-12
Anticipated expiration: 2040-10-13
Also published as: CN112210262B

Abstract

A heat-conducting coating and a preparation method thereof belong to the technical field of coatings. The heat-conducting coating comprises 15-60 wt% of water-based resin, 1-10 wt% of three-dimensional graphene, 0.2-2 wt% of dispersing agent and the rest water. The three-dimensional graphene includes a nano-carbon particle as a substrate and a graphene sheet vertically grown on a surface of the nano-carbon particle. The three-dimensional graphene with the special structure is mixed with the water-based resin to prepare the heat-conducting coating with the heat conductivity of more than 2.5W/m.k. Meanwhile, the three-dimensional graphene has the characteristic of isotropy, has excellent heat-conducting property in all directions, and can be used as a filler to be mixed with water-based resin to prepare the heat-conducting coating with excellent heat-conducting property.

Description

Heat-conducting coating and preparation method thereof

Technical Field

The application relates to the technical field of coatings, in particular to a heat-conducting coating and a preparation method thereof.

Background

With the rapid development of electronic technology and the increasing consumption demand of people, electronic products are developing towards the directions of high power, high integration and miniaturization, so that the working temperature of electronic devices is higher and higher, and if the heat conduction capability is insufficient, the working temperature of the electronic devices is greatly increased, and the performance, the stability and the service life of the devices are directly influenced. Therefore, the industry has raised higher requirements for the technologies of rapid heat dissipation of electronic devices, improvement of cooling and heat conduction efficiency and the like.

The traditional heat conduction method mainly comprises the steps of designing a cooling liquid circulation system, designing a heat conduction sheet structure and coating a heating connection part with a conductive paste. However, the design of the cooling system is not favorable for the miniaturization of equipment, and meanwhile, the cost is increased, and the safety and stability are poor.

The heat conducting coating is used for taking away heat generated by the device by utilizing physical heat radiation of the coating on the basis of not changing the structural design of the original device, and is an easy, effective, safe and reliable heat conducting scheme.

However, the coating has very low thermal conductivity and high thermal contact resistance with a heat-conducting substrate, and cannot realize the effect of accelerating the infrared radiation heat dissipation of the substrate.

The key point of the radiation heat-conducting coating is radiation heat-conducting filler, the current filler mainly comprises nano carbon spheres, carbon black, silicon carbide and the like, and the heat conductivity of the coating can be improved by adding the filler, so that the heat conductivity is improved. Due to the performances of high infrared emissivity, high thermal conductivity coefficient, high specific surface area and the like of the graphene, the graphene becomes an ideal heat-conducting additive material for the coating.

However, it is difficult for such a thermally conductive coating to have a thermal conductivity of 2.5W/m.k or more.

Disclosure of Invention

The application provides a heat-conducting coating and a preparation method thereof, which can provide the heat-conducting coating with the heat conductivity of more than 2.5W/m.k.

The embodiment of the application is realized as follows:

in a first aspect, the present application provides a thermally conductive coating material, which includes 15 to 60 wt% of an aqueous resin, 1 to 10 wt% of three-dimensional graphene, and 0.2 to 2 wt% of a dispersant, and the balance being water.

The three-dimensional graphene includes a nano-carbon particle as a substrate and a graphene sheet vertically grown on the surface of the nano-carbon particle.

In the technical scheme, the three-dimensional graphene with the special structure is mixed with the water-based resin to prepare the heat-conducting coating with the heat conductivity of more than 2.5W/m.k. Meanwhile, the three-dimensional graphene has the characteristic of isotropy, has excellent heat-conducting property in all directions, and can be used as a filler to be mixed with water-based resin to prepare the heat-conducting coating with excellent heat-conducting property.

The contact angle of the three-dimensional graphene is 148 degrees, and the three-dimensional graphene can be used as a hydrophobic material to be mixed with water-based resin to prepare a coating with good hydrophobic property. In addition, the three-dimensional graphene can fill gaps left when the aqueous resin is deposited to form a film, so that the coating is more compact. The corrosion of gas molecules and water molecules to a substrate coated with the coating is greatly reduced, so that the water resistance and the weather resistance of the heat-conducting coating are improved.

With reference to the first aspect, in a first possible example of the first aspect of the present application, the graphene sheet has an edge thickness of 1 to 3 atomic layers.

In a second possible example of the first aspect of the present application in combination with the first aspect, the above-mentioned aqueous resin includes any one or more of an aqueous epoxy resin, an aqueous acrylic resin, a acrylic emulsion, a silicone-acrylic emulsion, a styrene-acrylic emulsion, an amino resin, and a polyester resin.

In a third possible example of the first aspect of the present application in combination with the first aspect, the above-mentioned dispersant includes any one or more of hydroxymethyl cellulose, sodium methyl cellulose, sodium dodecylbenzene sulfonate, sodium deoxycholate, methyl cellulose, carboxymethyl cellulose, hydroxypropylmethyl cellulose, water-soluble polyacrylic acid, polyvinyl pyrrolidone, polyvinyl alcohol, and triton.

With reference to the first aspect, in a fourth possible example of the first aspect of the present application, the thermally conductive coating further includes a filler and an auxiliary agent.

Optionally, the auxiliary agent comprises any one or more of a defoamer, a leveling agent, a film forming aid, a thickener, a wetting agent, a rust inhibitor, a flash rust prevention aid, and a pH adjuster.

In a second aspect, the present application provides a method for preparing the above-mentioned heat conductive coating, which includes: mixing powdery three-dimensional graphene, an aqueous solution of an aqueous resin and a dispersant.

In the technical scheme, the preparation method of the heat-conducting coating is simple and convenient, and the prepared heat-conducting coating is stable.

In a first possible example of the second aspect of the present application, in combination with the second aspect, the three-dimensional graphene is prepared by vertically growing graphene sheets on the surface of a nano-carbon particle by a thermal chemical vapor deposition method.

With reference to the second aspect, in a second possible example of the second aspect of the present application, the three-dimensional graphene with a particle size of 100 to 500nm, the dispersant and water are mixed and ground to obtain a three-dimensional graphene slurry, and then the three-dimensional graphene slurry and an aqueous solution of an aqueous resin are mixed to obtain the thermal conductive coating.

Optionally, the particle size of the powdery three-dimensional graphene is 100-300 nm.

In the above example, grinding can improve the dispersibility of the three-dimensional graphene, so as to obtain a three-dimensional graphene slurry with good dispersibility.

With reference to the second aspect, in a third possible example of the second aspect of the present disclosure, the pH of the aqueous solution of the partial aqueous resin is adjusted to 9 to 10, the aqueous solution of the partial aqueous resin after the pH adjustment is mixed with a dispersant to prepare a first mixed solution, the first mixed solution and the powdered three-dimensional graphene are mixed and ground to prepare a second mixed solution, and then the second mixed solution is mixed with the remaining aqueous solution of the aqueous resin to prepare the thermal conductive coating.

In a fourth possible example of the second aspect of the present application in combination with the second aspect, the pH adjuster used in adjusting the pH of the aqueous solution of the aqueous resin is ammonia and/or triethanolamine.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.

Fig. 1 is a low-magnification SEM image of three-dimensional graphene according to an embodiment of the present application;

fig. 2 is a high power SEM image of three-dimensional graphene according to an embodiment of the present application;

fig. 3 is a TEM image of three-dimensional graphene according to an embodiment of the present application;

fig. 4 is a contact angle test chart of three-dimensional graphene according to an embodiment of the present disclosure;

FIG. 5 is a schematic view of a coating layer formed using the thermally conductive coating material according to an embodiment of the present application;

fig. 6 is an SEM image of a coating layer formed using the thermally conductive coating material according to an embodiment of the present application.

Detailed Description

Embodiments of the present application will be described in detail below with reference to examples, but those skilled in the art will appreciate that the following examples are only illustrative of the present application and should not be construed as limiting the scope of the present application. The examples, in which specific conditions are not specified, were conducted under 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.

The following is directed to a thermal conductive coating and a preparation method thereof according to embodiments of the present application. Specifically, the following description is made:

the application provides a heat-conducting coating, which comprises 15-60 wt% of water-based resin, 1-10 wt% of three-dimensional graphene, 0.2-2 wt% of a dispersing agent and the rest water.

The water-based resin is used as a matrix material, and the three-dimensional graphene is used as a filler.

Referring to fig. 1 to 3, the three-dimensional graphene has an isotropic characteristic and has excellent thermal conductivity in all directions, and the thermal conductive coating with thermal conductivity of more than 2.5W/m.k can be prepared by mixing the three-dimensional graphene as a filler with an aqueous resin.

The graphene layer at the edge of the three-dimensional graphene can be cross-bonded with the surface of the substrate coated with the coating, so that isotropy is presented, and excellent interface bonding is realized. However, the conventional graphene flakes are arranged in parallel between the coating and the substrate, become isotropic, and cannot be well embedded with the substrate.

As shown in fig. 4, the contact angle of the three-dimensional graphene is 148 °, and the thermal conductive coating prepared by mixing the three-dimensional graphene serving as a super-hydrophobic material with a water-based resin matrix also has good hydrophobic property. In addition, the three-dimensional graphene can fill gaps left when the aqueous resin is deposited to form a film, so that the coating is more compact. The corrosion of gas molecules and water molecules to a substrate coated with the coating is greatly reduced, so that the water resistance and the weather resistance of the heat-conducting coating are improved.

The three-dimensional graphene is prepared by the following method:

heating to 900-1500 ℃ at a heating rate of 1-10 ℃/min in an inert atmosphere by taking the nano carbon particles as a growth substrate, introducing a mixed atmosphere of hydrogen and methane, keeping the methane concentration at 10-50%, preserving the heat for 1-4 h, and cooling to room temperature to obtain the three-dimensional graphene powder.

Optionally, the particle size of the prepared three-dimensional graphene powder is 100-500 nm.

Optionally, the graphene sheet has an edge thickness of 1 to 3 atomic layers.

The method for preparing the three-dimensional graphene is simple and convenient, low in cost and capable of realizing industrial production.

The water-based resin comprises any one or more of water-based epoxy resin, water-based acrylic resin, pure acrylic emulsion, silicone acrylic emulsion, styrene-acrylic emulsion, amino resin and polyester resin.

In one embodiment of the present application, the aqueous resin may be an aqueous acrylic resin. In some other embodiments of the present application, the aqueous resin may also be an aqueous epoxy resin, acrylic emulsion, silicone-acrylic emulsion, styrene-acrylic emulsion, amino resin, or polyester resin alone, or a mixture of an aqueous epoxy resin and an aqueous acrylic resin, or a mixture of acrylic emulsion, silicone-acrylic emulsion, and styrene-acrylic emulsion, or a mixture of an amino resin and a polyester resin.

The dispersant comprises one or more of hydroxymethyl cellulose, sodium methylcellulose, sodium dodecyl benzene sulfonate, sodium deoxycholate, methylcellulose, carboxymethyl cellulose, hydroxypropyl methylcellulose, water-soluble polyacrylic acid, polyvinylpyrrolidone, polyvinyl alcohol and triton.

In one embodiment of the present application, the dispersant may be hydroxymethyl cellulose. In some other embodiments of the present application, the dispersant may also be sodium methyl cellulose, sodium dodecyl benzene sulfonate, sodium deoxycholate, methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, water soluble polyacrylic acid, polyvinyl pyrrolidone, polyvinyl alcohol, or triton, alone or in combination, with hydroxymethyl cellulose, sodium methyl cellulose, or in combination, with carboxymethyl cellulose, or in combination, with hydroxymethyl cellulose, polyvinyl pyrrolidone, or in combination, with water soluble polyacrylic acid, polyvinyl pyrrolidone, and polyvinyl alcohol.

Optionally, the heat-conducting coating comprises 15-60 wt% of water-based resin, 1-5 wt% of three-dimensional graphene, 0.2-2 wt% of dispersing agent and the balance of water.

Optionally, the heat-conducting coating comprises 15-60 wt% of water-based resin, 3 wt% of three-dimensional graphene, 0.2-2 wt% of dispersing agent and the balance of water.

The heat-conducting coating also comprises a filler and an auxiliary agent.

Optionally, the mass percentage of the filler in the heat-conducting coating is 10-15 wt%.

Optionally, the defoamer comprises a polyether siloxane copolymer and/or a mineral oil.

In one embodiment herein, the defoamer can be a polyether siloxane copolymer. In other embodiments herein, the defoamer can also be a mineral oil, or can be a mixture of a polyether siloxane copolymer and a mineral oil.

Optionally, the mass percentage of the defoaming agent in the heat-conducting coating is 0.1-1 wt%.

Optionally, the leveling agent comprises polyether modified polydimethylsiloxane and/or fluorine-containing acrylate copolymer.

In one embodiment of the present application, the leveling agent may be polyether-modified polydimethylsiloxane. In other embodiments of the present application, the leveling agent may also be a fluoroacrylate copolymer, or may be a mixture of polyether-modified polydimethylsiloxane and a fluoroacrylate copolymer.

Optionally, the mass percent of the leveling agent in the heat-conducting coating is 0.1-1 wt%.

Optionally, the coalescent comprises any one or more of dipropylene glycol methyl ether, propylene glycol methyl ether, and lauryl alcohol ester.

In one embodiment of the present application, the coalescent may be dipropylene glycol methyl ether. In other embodiments of the present application, the coalescent may also be propylene glycol methyl ether or lauryl alcohol ester alone, or a mixture of dipropylene glycol methyl ether, propylene glycol methyl ether, or a mixture of propylene glycol methyl ether, lauryl alcohol ester, or a mixture of dipropylene glycol methyl ether, propylene glycol methyl ether, and lauryl alcohol ester.

Optionally, the mass percentage of the film-forming aid in the heat-conducting coating is 3-5 wt%.

Optionally, the thickener comprises any one or more of fumed silica, an alkali swelling thickener, and a polyurethane thickener.

In one embodiment of the present application, the thickener may be fumed silica. In some other embodiments of the present application, the thickener may also be an alkali swelling thickener or a polyurethane thickener alone, or a mixture of fumed silica, an alkali swelling thickener, or a mixture of an alkali swelling thickener, a polyurethane thickener, or a mixture of fumed silica, an alkali swelling thickener, and a polyurethane thickener.

Optionally, the mass percentage of the thickener in the heat-conducting coating is 0.1-1 wt%.

Optionally, the wetting agent includes acetylenic diols and/or polyether siloxane copolymers.

In one embodiment of the present application, the wetting agent may be an acetylenic diol. In other embodiments of the present application, the wetting agent may also be a polyether siloxane copolymer, or a mixture of acetylenic diols, polyether siloxane copolymers.

Optionally, the mass percentage of the wetting agent in the heat-conducting coating is 0.1-1 wt%.

Optionally, the rust inhibitor comprises an aminocarboxylate and/or zinc phosphate.

In one embodiment of the present application, the rust inhibitor may be an aminocarboxylate. In other embodiments herein, the rust inhibitor may also be zinc phosphate, or may be a mixture of an aminocarboxylate and zinc phosphate.

Optionally, the mass percentage of the antirust agent in the heat-conducting coating is 0.1-1 wt%.

Optionally, the flash rust inhibitor additive comprises sodium nitrite and/or an amine adduct.

In one embodiment of the present application, the flash rust prevention aid may be sodium nitrite. In other embodiments of the present application, the flash rust inhibitor may also be an amine adduct, or a mixture of sodium nitrite and an amine adduct.

Optionally, the mass percentage of the flash rust prevention auxiliary agent in the heat-conducting coating is 1-3 wt%.

Optionally, the pH adjusting agent comprises ammonia and/or triethanolamine.

In one embodiment of the present application, the pH adjusting agent may be ammonia water. In other embodiments of the present application, the pH adjusting agent can also be triethanolamine, or a mixture of ammonia and triethanolamine.

Optionally, the mass percentage of the pH regulator in the heat-conducting coating is 0.1-1 wt%.

The application also provides a preparation method of the heat-conducting coating, which comprises the following steps: mixing powdery three-dimensional graphene, an aqueous solution of an aqueous resin and a dispersant.

Alternatively, the three-dimensional graphene is prepared by vertically growing graphene sheets on the surface of the nano-carbon particles by a thermal chemical vapor deposition method.

Specifically, the heat conductive coating includes two preparation methods.

The first preparation method is as follows:

1. preparation of three-dimensional graphene slurry

Mixing powdery three-dimensional graphene with the particle size of 100-500 nm, a dispersing agent and water, dispersing for at least 10min by using a high-speed dispersion machine to prepare a three-dimensional graphene dispersion liquid, and then injecting the three-dimensional graphene dispersion liquid into a sand mill to grind for at least 10min to prepare a three-dimensional graphene slurry;

Optionally, the rotating speed of the high-speed dispersion machine is 500-1500 r/min;

optionally, the rotation speed of the sand mill is 2000-3000 r/min.

2. Preparation of Heat-conducting coating

Mixing the prepared three-dimensional graphene slurry, water-based resin, filler and an auxiliary agent, dispersing for at least 10min by using a high-speed dispersion machine, standing and defoaming to prepare a heat-conducting coating;

optionally, the rotating speed of the high-speed dispersion machine is 500-1500 r/min.

The second preparation method is as follows:

1. preparation of an aqueous resin Dispersion

Mixing part of aqueous resin, a dispersant and water, and dispersing for at least 10min by using a high-speed dispersion machine for the first time to prepare an aqueous resin solution, adjusting the pH of the aqueous resin solution to 9-10 by using a pH regulator, and dispersing for at least 5min by using the high-speed dispersion machine for the second time to prepare an aqueous resin dispersion liquid;

optionally, the rotating speed of the high-speed dispersing machine during the first dispersing is 300-500 r/min;

optionally, the rotating speed of the high-speed disperser in the second dispersing is 500-800 r/min.

2. Preparation of Heat-conducting coating

Mixing an aqueous solution of aqueous resin with the pH value of 9-10, three-dimensional graphene powder, a filler and part of auxiliaries, dispersing for at least 10min with a high-speed dispersion machine for the third time to obtain a first dispersion liquid, injecting the first dispersion liquid into a sand mill, grinding for at least 10min until the fineness of the first dispersion liquid is less than or equal to 35 mu m to obtain a second dispersion liquid, mixing the second dispersion liquid and the rest of aqueous resin, dispersing for at least 10min with the high-speed dispersion machine for the fourth time, adding the rest of auxiliaries, and dispersing for at least 10min with the high-speed dispersion machine for the fifth time to obtain the heat-conducting coating;

optionally, the rotating speed of the high-speed dispersion machine during the third dispersion, the fourth dispersion and the fifth dispersion is 300-800 r/min;

optionally, the rotation speed of the sand mill is 1000-3000 r/min.

A thermally conductive coating and a method for preparing the same according to the present application will be described in further detail with reference to the following examples.

Example 1

The embodiment of the application provides a heat-conducting coating and a preparation method thereof, and the heat-conducting coating comprises the following steps:

1. preparation of three-dimensional graphene slurry

Mixing three-dimensional graphene powder, polyvinylpyrrolidone, hydroxymethyl cellulose and water, dispersing for 2 hours by a high-speed dispersion machine at the rotating speed of 1200r/min to prepare a three-dimensional graphene dispersion liquid, and then injecting the three-dimensional graphene dispersion liquid into a sand mill at the rotating speed of 2200r/min for grinding for at least 10min to prepare a three-dimensional graphene slurry;

2. preparation of Heat-conducting coating

Mixing the prepared three-dimensional graphene slurry, water-based acrylic resin, amino carboxylate and fluorine-containing acrylate, dispersing for 2 hours by using a high-speed dispersion machine at the rotating speed of 1500r/min, standing and defoaming to prepare the heat-conducting coating.

The heat-conducting coating comprises, by mass, 3% of three-dimensional graphene powder, 20% of water-based acrylic resin, 1% of polyvinylpyrrolidone and hydroxymethyl cellulose, 0.1% of amino carboxylate and 0.1% of fluorine-containing acrylate.

Example 2

1. preparation of an aqueous resin Dispersion

Mixing half of styrene-acrylic emulsion, sodium dodecyl benzene sulfonate and water, performing first dispersion for 10min at the rotating speed of 500r/min by using a high-speed dispersion machine to prepare an aqueous solution of the styrene-acrylic emulsion, adjusting the pH of the aqueous solution of the styrene-acrylic emulsion to 9.5 by using ammonia water, and performing second dispersion for 10min at the rotating speed of 500r/min by using the high-speed dispersion machine to prepare a dispersion liquid of the styrene-acrylic emulsion;

2. preparation of Heat-conducting coating

Mixing an aqueous solution of a styrene-acrylic emulsion with the pH value of 9.5, three-dimensional graphene powder, aminocarboxylate and fluorine-containing acrylate, dispersing for 10min at the rotating speed of 500r/min for the third time by using a high-speed dispersion machine to prepare a first dispersion liquid, injecting the first dispersion liquid into a sand mill, grinding for 30min at the rotating speed of 2000r/min until the fineness of the first dispersion liquid is less than or equal to 35um to prepare a second dispersion liquid, mixing the second dispersion liquid and the rest half of the styrene-acrylic emulsion, dispersing for 10min at the rotating speed of 500r/min for the fourth time by using the high-speed dispersion machine, adding polyether siloxane copolymer, dispersing for 10min at the rotating speed of 500r/min for the fifth time by using the high-speed dispersion machine, and adding fumed silica to prepare;

the heat-conducting coating comprises, by mass, 3% of three-dimensional graphene powder, 20% of styrene-acrylic emulsion, 1% of sodium dodecyl benzene sulfonate, 0.1% of aminocarboxylate, 0.1% of fluoroacrylate, 0.1% of polyether siloxane copolymer and 0.1% of fumed silica, wherein the content of the three-dimensional graphene powder in the heat-conducting coating is 3%, the content of the styrene-acrylic emulsion is 20%, the content of the sodium dodecyl benzene sulfonate is 1%, the content of the aminocarboxylate is 0.1%, the content.

Example 3

1. preparation of three-dimensional graphene slurry

2. preparation of Heat-conducting coating

Wherein, the mass percent of the three-dimensional graphene powder in the heat-conducting coating is 1%, the mass percent of the water-based acrylic resin is 20%, the sum of the mass percent of the polyvinylpyrrolidone and the mass percent of the hydroxymethyl cellulose is 1%, the mass percent of the amino carboxylate is 0.1%, and the mass percent of the fluorine-containing acrylate is 0.1%.

Example 4

1. preparation of three-dimensional graphene slurry

2. preparation of Heat-conducting coating

The heat-conducting coating comprises, by mass, 10% of three-dimensional graphene powder, 20% of water-based acrylic resin, 1% of polyvinylpyrrolidone and hydroxymethyl cellulose, 0.1% of amino carboxylate and 0.1% of fluorine-containing acrylate.

Comparative example 1

The application provides a heat-conducting coating and a preparation method thereof, and the heat-conducting coating comprises the following steps:

mixing water-based acrylic resin, polyvinylpyrrolidone, hydroxymethyl cellulose, water, aminocarboxylate and fluorine-containing acrylate, dispersing for 2h at the rotating speed of 1500r/min by using a high-speed dispersion machine, standing and defoaming to obtain the heat-conducting coating.

Wherein, the mass percent of the water-based acrylic resin in the heat-conducting coating is 20%, the sum of the mass percent of the polyvinylpyrrolidone and the mass percent of the hydroxymethyl cellulose is 1%, the mass percent of the amino carboxylate is 0.1%, and the mass percent of the fluorine-containing acrylate is 0.1%.

Comparative example 2

1. preparation of graphene slurry

Mixing flake graphene powder, polyvinylpyrrolidone, hydroxymethyl cellulose and water, dispersing for 2 hours by a high-speed dispersion machine at the rotating speed of 1200r/min to prepare flake graphene dispersion liquid, and then injecting the flake graphene dispersion liquid into a sand mill at the rotating speed of 2200r/min for grinding for at least 10 minutes to prepare flake graphene slurry;

2. preparation of Heat-conducting coating

Mixing the prepared sheet graphene slurry, water-based acrylic resin, amino carboxylate and fluorine-containing acrylate, dispersing for 2 hours by using a high-speed dispersion machine at the rotating speed of 1500r/min, standing and defoaming to prepare the heat-conducting coating.

Wherein, the mass percent of the flaky graphene powder in the heat-conducting coating is 3%, the mass percent of the water-based acrylic resin is 20%, the sum of the mass percent of the polyvinylpyrrolidone and the mass percent of the hydroxymethyl cellulose is 1%, the mass percent of the amino carboxylate is 0.1%, and the mass percent of the fluorine-containing acrylate is 0.1%.

Comparative example 3

1. preparation of three-dimensional graphene slurry

2. preparation of Heat-conducting coating

The heat-conducting coating comprises, by mass, 0.5% of three-dimensional graphene powder, 20% of water-based acrylic resin, 1% of polyvinylpyrrolidone and hydroxymethyl cellulose, 0.1% of aminocarboxylate and 0.1% of fluorine-containing acrylate.

Comparative example 4

1. preparation of three-dimensional graphene slurry

2. preparation of Heat-conducting coating

Wherein the mass percent of the three-dimensional graphene powder in the heat-conducting coating is 15%, the mass percent of the water-based acrylic resin is 20%, the sum of the mass percent of the polyvinylpyrrolidone and the mass percent of the hydroxymethyl cellulose is 1%, the mass percent of the amino carboxylate is 0.1%, and the mass percent of the fluorine-containing acrylate is 0.1%.

It should be noted that the three-dimensional graphene used in examples 1 to 4 and comparative examples 1 to 4 is prepared by vertically growing graphene sheets on the surface of a carbon nanoparticle by a thermal chemical vapor deposition method.

Comparative example 5

1. preparation of three-dimensional graphene slurry

The three-dimensional graphene of the comparative example is prepared by a template method, methane is used as a carbon source, and graphene grows on the surface of a nickel screen at the temperature of 900-1000 ℃ to obtain the graphene-nickel screen compound. And etching the nickel screen, and freeze-drying to obtain the three-dimensional graphene used in the comparative example.

2. Preparation of Heat-conducting coating

Test example 1

The heat-conducting coatings prepared in examples 1 to 4 and comparative examples 1 to 5 are uniformly coated on the surface of an electronic device by adopting a spraying mode, and the coating thickness is 20 to 40um, please refer to fig. 5 and 6. The infrared radiance of the coating is tested by the method of the national standard GB 4653-1984, the thermal conductivity of the coating is tested by a transient plane heat source method thermal conductivity coefficient tester, and the adhesive force of the coating is tested by the method of the national standard GB 5210-2006. The test results are shown in table 1.

TABLE 1 Heat-conductive coating Properties of examples 1 to 4 and comparative examples 1 to 5

Item	Infrared emissivity (%)	Thermal conductivity (W/m.k)	Adhesion (MPa)
				Example 1	96	3.2	6.5
Example 2	96	3.3	6.4
				Example 3	95	3.1	6.2
Example 4	96	3.3	5.9
				Comparative example 1	90	0.3	6.0
Comparative example 2	95	2.3	5.8
				Comparative example 3	94	2.6	6.0
Comparative example 4	96	3.5	4.6
				Comparative example 5	95	2.5	6.2

From comparison of example 1 and comparative example 1, it is known that a coating material having excellent thermal conductive properties can be obtained by mixing three-dimensional graphene as a filler with an aqueous resin.

As can be seen from comparison between example 1 and comparative example 2, the structure of the graphene flake powder results in a thermal conductivity of 2.5W/m.k or less in the thermal conductive coating prepared using the graphene flake powder as a filler.

As can be seen from comparison between example 1 and comparative example 3, the thermal conductivity of the thermally conductive coating is significantly reduced when the amount of three-dimensional graphene is small.

As can be seen from comparison between example 1 and comparative example 4, when the amount of three-dimensional graphene is large, although the infrared radiance and the thermal conductivity of the thermal conductive coating still have good performance, the adhesive force is low, so that the thermal conductive coating cannot be well attached to an electronic device.

As can be seen from comparison of example 1 and comparative example 5, the thermal conductivity of the thermally conductive coating was poor due to severe cross-linking of the three-dimensional graphenes prepared by the template method. Meanwhile, the existing three-dimensional graphene is mainly manufactured by a template method, the manufacturing process is complex, industrial waste liquid can be generated, the preparation cost is high, and large-scale production is not facilitated.

In conclusion, the three-dimensional graphene with the special structure can be mixed with the water-based resin to prepare the heat-conducting coating with the heat conductivity of more than 2.5W/m.k. Meanwhile, the three-dimensional graphene has the characteristic of isotropy, has excellent heat-conducting property in all directions, and can be used as a filler to be mixed with water-based resin to prepare the heat-conducting coating with excellent heat-conducting property. Meanwhile, the three-dimensional graphene has the characteristic of isotropy, has excellent heat-conducting property in all directions, and can be used as a filler to be mixed with water-based resin to prepare the heat-conducting coating with excellent heat-conducting property. The contact angle of the three-dimensional graphene is 148 degrees, and the three-dimensional graphene can be used as a hydrophobic material to be mixed with water-based resin to prepare a coating with good hydrophobic property. In addition, the three-dimensional graphene can fill gaps left when the aqueous resin is deposited to form a film, so that the coating is more compact. The corrosion of gas molecules and water molecules to a substrate coated with the coating is greatly reduced, so that the water resistance and the weather resistance of the heat-conducting coating are improved.

The foregoing is illustrative of the present application and is not to be construed as limiting thereof, as numerous modifications and variations will be apparent to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. The heat-conducting coating is characterized by comprising 15-60 wt% of water-based resin, 1-10 wt% of three-dimensional graphene, 0.2-2 wt% of a dispersing agent and the rest water;

the three-dimensional graphene includes a nano-carbon particle as a substrate and a graphene sheet vertically grown on a surface of the nano-carbon particle.

2. The heat conductive coating of claim 1, wherein the graphene sheets have an edge thickness of 1 to 3 atomic layers.

3. The heat conductive coating of claim 1 or 2, wherein the aqueous resin comprises any one or more of an aqueous epoxy resin, an aqueous acrylic resin, a pure acrylic emulsion, a silicone acrylic emulsion, a styrene acrylic emulsion, an amino resin, and a polyester resin.

4. The heat conductive coating of claim 1 or 2, wherein the dispersant comprises any one or more of hydroxymethyl cellulose, sodium methyl cellulose, sodium dodecylbenzenesulfonate, sodium deoxycholate, methyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, water-soluble polyacrylic acid, polyvinyl pyrrolidone, polyvinyl alcohol, and triton.

5. The heat conductive coating material according to claim 1 or 2, further comprising a filler and an auxiliary agent;

optionally, the auxiliary agent comprises any one or more of a defoaming agent, a leveling agent, a film forming auxiliary agent, a thickening agent, a wetting agent, a rust inhibitor, a flash rust prevention auxiliary agent and a pH adjusting agent.

6. The preparation method of the heat-conducting coating as claimed in any one of claims 1 to 5, wherein the preparation method of the heat-conducting coating comprises the following steps: mixing the three-dimensional graphene in a powder state, the aqueous solution of the aqueous resin, and the dispersant.

7. The method for preparing the heat-conducting coating according to claim 6, wherein the three-dimensional graphene is prepared by vertically growing graphene sheets on the surface of the nano-carbon particles by a thermal chemical vapor deposition method.

8. The preparation method of the heat-conducting coating according to claim 6 or 7, wherein the heat-conducting coating is prepared by mixing and grinding powdery three-dimensional graphene with the particle size of 100-500 nm, the dispersing agent and water to obtain three-dimensional graphene slurry, and then mixing the three-dimensional graphene slurry and the aqueous solution of the water-based resin;

9. The method for preparing the heat-conducting paint according to claim 6 or 7, wherein the pH of part of the aqueous solution of the aqueous resin is adjusted to 9-10, the part of the aqueous solution of the aqueous resin after the pH adjustment is mixed with the dispersant to prepare a first mixed solution, the first mixed solution and the powdery three-dimensional graphene are mixed and ground to prepare a second mixed solution, and then the second mixed solution is mixed with the rest of the aqueous solution of the aqueous resin to prepare the heat-conducting paint.

10. The method for preparing a heat conductive coating according to claim 9, wherein the pH adjuster used for adjusting the pH of the aqueous solution of the aqueous resin is ammonia and/or triethanolamine.