CN113637326B - A kind of preparation method for the graphene additive of heat-conducting silica gel material - Google Patents

Abstract

The invention discloses a method for preparing a graphene additive for thermally conductive silica gel materials. The graphene additive is graphene powder obtained by reducing a graphene oxide solution with a special reducing agent. The preparation method of the graphene additive includes The following steps: S1: heat up the graphene oxide solution to 50-60°C; S2: slowly add a special reducing agent to the graphene oxide solution, and react for 23-25 hours in a water bath at 65-75°C; The obtained solution is subjected to centrifugation, the solution is washed to neutrality, and finally vacuum-dried to obtain graphene additive powder. The present invention reduces graphene oxide by adding a special reducing agent, so that the graphene microsheet structure contains functional groups, which improves the phenomenon of poor dispersion and serious agglomeration of common graphene in thermally conductive silica gel, so that graphene additives can be used in thermally conductive silica gel Good uniform dispersion in the silicone oil matrix effectively improves the thermal conductivity of the thermally conductive silicone material.

Description

A kind of preparation method for the graphene additive of heat-conducting silica gel material

technical field

The invention belongs to the technical field of heat-conducting silica gel, and in particular relates to a method for preparing a graphene additive used in heat-conducting silica gel materials.

Background technique

With the rapid development of modern electronic equipment and semiconductor facilities such as LEDs, the demand and difficulty of manufacturing heat-conducting materials are getting higher and higher. Due to its own properties, the traditional thermal conductive silicone grease material will reduce the thermal conductivity as the material volatilizes, thereby affecting the performance of the component. Thermally conductive silica gel is a thermal interface material composed of a silica gel matrix and a thermally conductive filler. It is used in electronic products including LED lamps due to its good thermal conductivity, flexibility, stability, and natural surface adhesion. device.

As a composite thermal interface material, thermally conductive silica gel has poor thermal conductivity of the silica gel matrix, so it is necessary to add thermally conductive fillers to improve its thermal conductivity. Generally, copper, aluminum, aluminum oxide, aluminum nitride, silicon carbide and other thermally conductive fillers are widely used in the market. The thermally conductive fillers are filled with the same volume fraction or mass fraction of the thermally conductive silica gel matrix. The higher the thermal conductivity, the better the thermal conductivity of the composite material. The performance is more excellent, so the filler with higher thermal conductivity can be used to prepare composite materials with higher thermal conductivity. As a new type of thermally conductive filler, graphene has the advantages of ultra-high carrier mobility, excellent thermal conductivity, high specific surface area, and high flexibility. The thermally conductive graphene-based thermally conductive material has far better thermal conductivity than interface thermally conductive materials prepared with other traditional fillers.

At present, most of the common graphene in the market cannot be well dispersed in the silica gel matrix, which makes the heat conduction of the material uneven, and also has mutual repulsion with the components of the heat conduction silica gel, which affects the curing time and viscosity of the material. Therefore need to invent a kind of graphene additive that is suitable for heat-conducting silica gel material.

Contents of the invention

In order to overcome the deficiencies of the prior art, the present invention provides a method for preparing a graphene additive for thermally conductive silica gel materials.

In order to achieve the above object, the present invention adopts the following technical scheme: a kind of preparation method for the graphene additive of heat-conducting silica gel material, and this graphene additive is the graphene powder obtained by reducing graphene oxide solution by special reductant, so The preparation method of described graphene additive comprises the following steps:

S1: heating the graphene oxide solution to 50-60°C;

S2: Slowly add a special reducing agent to the graphene oxide solution, and react for 23-25 hours in a water bath at 65-75°C;

S3: After the reaction is completed, the obtained solution is centrifuged, the solution is washed until neutral, and finally vacuum-dried to obtain graphene additive powder.

Optionally, the special reducing agent is set as R-based hydrazine, wherein R is an alkyl group of 1-8 and its isomers, and its molecular structure is:

Optionally, the special reducing agent includes one or more of tert-butylhydrazine, methylhydrazine, and octylhydrazine.

Optionally, the preparation method of the special reducing agent is as follows:

ⅠIn the synthesis device, add concentrated sulfuric acid and urea, and react in an ice bath at 15-25°C for 1-3 hours, and the molar ratio is 2:1;

Ⅱ Slowly add R alcohol dropwise to the synthesis device, the molar ratio of R alcohol to urea is 1:1, keep the reaction at 20-25°C for 3-5 hours, then let stand at room temperature for 15-17 hours, then add Neutralize the pH to 3-4 with ammonia water, filter and dry to obtain white crystal R-urea;

Ⅲ Dissolve the R-based urea in ethanol, then add the ethanol solution containing chlorine gas dropwise to the device, and react at 14-16°C for 0.2-1 hour after the dropwise addition, wherein the molar ratio of chlorine gas to R-based urea is 1.05:1.0 ;

Ⅳ Dissolve NaOH in water to form an aqueous solution and slowly add it dropwise into the device, and keep it at 4-6°C for 0.5-1.5 hours. The molar ratio of NaOH to R-urea is 4.5-5.0:1.0, and then filter the reaction solution. Heating the filtrate and taking the distillate at 100-104°C to obtain the special reducing agent R-based hydrazine.

Optionally, the reaction process for preparing the special reducing agent is:

Optionally, in the S1, the temperature of the graphene oxide solution is raised to 55°C. After the graphene oxide solution is heated up, it is more conducive to the reduction reaction in the next step.

Optionally, the volume ratio of the graphene oxide solution to the special reducing agent in S2 is 1:10-15.

Optionally, the dropping rate of the special reducing agent in S2 is 0.1-0.12mL/s.

Optionally, the vacuum drying temperature in S3 is -11-9°C, and the drying time is 70-74 hours.

Optionally, the centrifugation speed of the centrifugation in S3 is 8000-10000r/min.

In summary, the beneficial effects of the present invention are:

In the process of reducing graphene oxide, the special reducing agent makes the graphene microsheet structure contain functional groups. This special oxygen-containing functional group can be better connected with long chains of organic substances such as silica gel, so that the two can be combined more effectively. Improves the phenomenon of poor dispersion and serious agglomeration of common graphene in thermal silica gel, so that the graphene additive can be well and uniformly dispersed in the silicone oil matrix of thermal silica gel, making the heat dissipation of the material smoother, and effectively improving the thermal conductivity of the thermal silica gel material , Tensile strength, optimize the curing time and material viscosity of thermal silica gel, so that thermal silica gel can be better used as thermal interface composite material.

Detailed ways

Below in conjunction with specific embodiment, further illustrate the present invention. It should be understood that these examples are for illustration only and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the teachings of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of the present application.

A preparation method for a graphene additive for thermally conductive silica gel material, comprising the following steps:

S1: heating the graphene oxide solution to 50-60°C;

S2: Slowly add a special reducing agent to the graphene oxide solution, and react for 20-28 hours in a water bath at 65-75°C; the graphene oxide solution is added dropwise using a separatory funnel;

S3: After the reaction is completed, the obtained solution is centrifuged, the solution is washed until neutral, and finally vacuum-dried to obtain graphene additive powder.

The special reducing agent is set as R-based hydrazine, wherein R is an alkyl group of 1-8 and its isomers, and the special reducing agent includes one of tert-butylhydrazine, methylhydrazine, and octylhydrazine or more.

Wherein, the preparation method of special reducing agent is as follows:

ⅠIn the synthesis device, add concentrated sulfuric acid and urea, and react in an ice bath at 15-25°C for 1-3 hours, and the molar ratio is 2:1;

Ⅱ Slowly add R alcohol dropwise to the synthesis device, the molar ratio of the R alcohol to urea is 1:1, keep the reaction at 20-25°C for 2-6 hours, then let stand at room temperature for 12-20 hours, then add Neutralize the pH to 3-4 with ammonia water, filter and dry to obtain white crystal R-urea;

Ⅲ Dissolve the R-based urea in ethanol, then add the ethanol solution containing chlorine gas dropwise to the device, and react at 10-20°C for 0.2-1 hour after the dropwise addition, wherein the molar ratio of chlorine gas to R-based urea is 1.05:1.0 ;

Ⅳ Dissolve NaOH in water to form an aqueous solution and slowly add it dropwise into the device, and keep it at 2-10°C for 0.5-2 hours. The molar ratio of NaOH to R-urea is 4.5-5.0:1.0, and then filter the reaction solution. Heating the filtrate and taking the distillate at 100-104°C to obtain the special reducing agent R-based hydrazine.

The volume ratio of the graphene oxide solution to the special reducing agent in S2 is 1:10-15.

The dropping rate of the special reducing agent in S2 is 0.1-0.12mL/s.

The vacuum drying temperature in S3 is -10°C, and the drying time is 72 hours.

The centrifugal speed of the centrifugal separation in S3 is 8000-10000r/min.

Example 1

The special reducing agent used in this example is tert-butylhydrazine.

1. Production process

A preparation method for a graphene additive for thermally conductive silica gel material, comprising the following steps:

S1a: heating the graphene oxide solution to 55°C;

S2a: Slowly add a special reducing agent to the graphene oxide solution, and react in a water bath at 70°C for 24 hours;

S3a: Centrifuge the obtained solution after the reaction is completed, wash the solution to neutrality, and finally vacuum-dry to obtain graphene additive powder.

Wherein, the special reducing agent described in step S2a is tert-butylhydrazine, and its specific preparation method is as follows:

(1-1) In the synthesis device, add 193g of concentrated sulfuric acid (98.5% by mass) and 60g of finely ground urea, and react in an ice bath at 15°C for 2 hours, with a molar ratio of 2:1;

(1-2) Slowly add 74g of tert-butanol dropwise to the synthesis device, wherein the molar ratio of tert-butanol to urea is 1:1, and the reaction is kept at 24°C for 4 hours to complete the dropwise addition, and left to stand at room temperature for 16 hours. Then add ammonia water to neutralize the pH to 3-4, filter and dry to obtain white crystal tert-butylurea;

(1-3) Dissolve 10g of tert-butyl urea in ethanol, control the temperature at 15°C, then add dropwise 19mL of ethanol solution containing 6.4g of chlorine gas into the device, and react at 15°C for half an hour after the addition, to control the chlorine gas The molar ratio with tert-butylurea is 1.05:1;

(1-4) Slowly add 16.4g of NaOH dissolved in 160mL of water to the device in an ice bath at 5°C to form an aqueous solution, wherein the molar ratio of NaOH to tert-butylurea is 4.6:1, and it takes about one hour to complete the drop , continue to stir and react for half an hour, then filter the reaction solution, heat the filtrate to take a fraction at 100-104°C to obtain an aqueous solution of tert-butylhydrazine.

The concentration of the graphene oxide solution described in step S1a is 6g/L.

The volume ratio of the graphene oxide solution described in step S2a to tert-butylhydrazine is 1:12.

Slowly add the special reducing agent described in step S2a, the specific dropping rate is 0.1mL/s.

For the centrifugal separation described in step S3a, the specific centrifugal speed is 10000r/min.

For the vacuum drying described in step S3a, the temperature should be controlled at -10°C, and the drying time should be 72 hours.

2. Results analysis

Add the obtained graphene additive to one of the components of the two-component addition type thermally conductive silica gel, which can be well dispersed in the system as a filler, and the obtained thermally conductive silica gel, after being mixed and cured by components A and B, As shown in Table 1, the thermal conductivity increased by 10% and the tensile strength increased by 15%.

Example 2

In this embodiment, the special reducing agent adopts methylhydrazine.

1. Production process

A preparation method for a graphene additive for thermally conductive silica gel material, comprising the following steps:

S1b: heating the graphene oxide solution to 58°C;

S2b: Slowly add a special reducing agent to the graphene oxide solution, and react in a water bath at 72°C for 24 hours;

S3b: Centrifuge the obtained solution after the reaction is completed, wash the solution until neutral, and finally vacuum-dry to obtain graphene additive powder.

Wherein, the special reducing agent described in step S2b is methylhydrazine, and its specific preparation method is as follows:

(2-1) In the synthesis device, add 193g of concentrated sulfuric acid (98.5% by mass) and 60g of finely ground urea, and react in an ice bath at 15°C for 2 hours, and the molar ratio is 2:1;

(2-2) Slowly add 32g of methanol dropwise to the synthesis device, wherein the molar ratio of methanol to urea is 1:1, keep warm at 24°C for 4 hours to complete the dropwise reaction, let stand at room temperature for 16 hours, and then add ammonia water and pH to 3-4, filtered and dried to obtain white crystal methyl urea;

(2-3) In the synthesis device, dissolve 6.4g of methylurea at 15°C, control the temperature at 10°C, then add dropwise 19ml of ethanol solution containing 6.4g of chlorine gas into the device, and finish the addition at 10°C React for half an hour, and control the molar ratio of chlorine to methylurea to be 1.05:1;

(2-4) Slowly add 16.4g of NaOH dissolved in 160ml of water to the device in an ice bath at 5°C to form an aqueous solution, wherein the molar ratio of NaOH to methylurea is 4.3:1, and it takes about one hour to complete the dripping. Continue to stir and react for half an hour, then filter the reaction solution, heat the filtrate to obtain a fraction at 80-90°C to obtain an aqueous solution of methylhydrazine.

The concentration of the graphene oxide solution described in step S1b is 3g/L.

The volume ratio of the graphene oxide solution and methylhydrazine described in step S2b is 1:15.

Slowly add the special reducing agent described in step S2b, the specific dropping rate is 0.1mL/s.

For the centrifugal separation described in step S3b, the specific centrifugal speed is 8000r/min.

For the vacuum drying described in step S3b, the temperature should be controlled at -10°C, and the drying time should be 72 hours.

2. Results analysis

Add the obtained graphene additive to one of the components of the two-component addition type thermally conductive silica gel, which can be well dispersed in the system as a filler, and the obtained thermally conductive silica gel, after being mixed and cured by components A and B, As shown in Table 1, the thermal conductivity increased by 8.5%, and the tensile strength increased by 12.8%.

Example 3

The special reducing agent used in this embodiment is octylhydrazine.

1. Production process

A preparation method for a graphene additive for thermally conductive silica gel material, comprising the following steps:

S1c: heating the graphene oxide solution to 55°C;

S2c: Slowly add a special reducing agent to the graphene oxide solution, and react for 24 hours in a water bath at 75°C;

S3c: Centrifuge the obtained solution after the reaction is completed, wash the solution until neutral, and finally vacuum-dry to obtain graphene additive powder.

Wherein, the special reducing agent described in step S2c is octylhydrazine, and its specific preparation method is as follows:

(3-1) In the synthesis device, add 193g of concentrated sulfuric acid (98.5% by mass) and 60g of finely ground urea, and react for 2 hours under ice bath conditions at 15°C, and the molar ratio is 2:1;

(3-2) Slowly add 130g of octanol dropwise to the synthesis device, wherein the molar ratio of octanol to urea is 1:1, keep the reaction at 20°C for 4 hours to complete the dropwise addition, let it stand at room temperature for 16 hours, and then add Neutralize pH to 3-4 with ammonia water, filter and dry to obtain white crystal octyl urea;

(3-3) Dissolve 14.8g of octyl urea in ethanol, control the temperature at 15°C, then add dropwise 19mL ethanol solution containing 6.4g of chlorine gas into the device, and react at 15°C for half an hour after the addition, to control the chlorine gas The molar ratio with octyl urea is 1.05:1;

(3-4) Slowly add 16.4g NaOH dissolved in 160mL water to the device in an ice bath at 5°C to form an aqueous solution, wherein the molar ratio of NaOH to octyl urea is 4.8:1, and it takes about one hour to complete the dripping. Continue to stir and react for half an hour, then filter the reaction solution, heat the filtrate to obtain a fraction at 100-104°C, an aqueous solution of octylhydrazine.

The concentration of the graphene oxide solution described in step S1c is 8g/L.

The volume ratio of the graphene oxide solution and octylhydrazine described in step S2c is 1:10.

Slowly add the special reducing agent described in step S2c, the specific dropping rate is 0.1ml/s.

For the centrifugal separation described in step S3c, the specific centrifugal speed is 10000r/min.

For the vacuum drying described in step S3c, the temperature should be controlled at -10°C, and the drying time should be 72 hours.

2. Results Analysis

Add the obtained graphene additive to one of the components of the two-component addition type thermally conductive silica gel, which can be well dispersed in the system as a filler, and the obtained thermally conductive silica gel, after being mixed and cured by components A and B, As shown in Table 1, the thermal conductivity increased by 6%, and the tensile strength increased by 16.9%.

Comparative example 1

Without adding any graphene additives to the two-component addition-type thermally conductive silica gel, the resulting thermally conductive silica gel is unsatisfactory in terms of thermal conductivity and tensile strength, as shown in Table 1, after being mixed and cured with components A and B.

Comparative example 2

Graphene 1 purchased on the market, which uses graphene products from Nanjing Xianfeng Nano Material Technology Co., Ltd., is added as a graphene additive to one of the components of the two-component addition type thermally conductive silica gel, and cannot be used as a filler It is well dispersed in the system, and there are obvious agglomerated particles in the system, and after the obtained thermal conductive silica gel has experienced the mixing and curing of components A and B, as shown in Table 1, the thermal conductivity is only increased by 0.5%, and the tensile strength 23.1% lower.

Comparative example 3

The graphene 2 purchased on the market, which is a product of XG Sciences, is added as a graphene additive to one of the components of the two-component addition type thermally conductive silica gel, which cannot be well dispersed in the system as a filler , there are obvious agglomerated particles in the system, and after the obtained thermally conductive silica gel undergoes mixing and curing of components A and B, as shown in Table 1, the thermal conductivity is only increased by 1.5%, and the tensile strength is reduced by 17.3%.

The performance comparison of the thermally conductive silica gel prepared by each embodiment and comparative example of table 1

Among them, the thermal conductivity meter coefficient is tested by using the DTC-300 thermal conductivity meter of TA Instruments in the United States; the tensile strength test is obtained by using the universal electronic tensile testing machine Z003.

The implementation methods described above do not constitute a limitation to the scope of protection of the technical solution. Any modifications, equivalent replacements and improvements made within the spirit and principles of the above implementation methods shall be included in the protection scope of the technical solution.

Claims (9)

1. A preparation method of a graphene additive for a heat-conducting silica gel material is characterized in that the graphene additive is graphene powder obtained by reducing a graphene oxide solution by a special reducing agent, and the preparation method of the graphene additive comprises the following steps:

s1: heating the graphene oxide solution to 50-60 ℃;

s2: slowly adding a special reducing agent into the graphene oxide solution, and reacting for 23-25 hours at 65-75 ℃ under the water bath condition;

s3: after the reaction is finished, carrying out centrifugal separation on the obtained solution, washing the solution to be neutral, and finally carrying out vacuum drying to obtain graphene additive powder;

the special reducing agent is R-based hydrazine, wherein R is alkyl of 1-8 and isomers thereof, and the molecular structure of the special reducing agent is as follows:

2. the method as claimed in claim 1, wherein the specific reducing agent comprises one or more of tert-butyl hydrazine, methyl hydrazine and octyl hydrazine.

3. The method for preparing the graphene additive for the heat-conducting silica gel material according to claim 1, wherein the specific reducing agent is prepared by the following steps:

adding concentrated sulfuric acid and urea into a synthesis device, and reacting for 1-3 hours at 15-25 ℃ under an ice bath condition, wherein the molar ratio is 2:1;

II, slowly dripping R alcohol into the synthesis device, wherein the molar ratio of the R alcohol to the urea is 1:1, reacting for 3-5 hours at the temperature of 20-25 ℃, standing for 15-17 hours at room temperature, adding ammonia water to neutralize the pH value to 3-4, filtering and drying to obtain white crystal R-based urea;

III, dissolving R-urea in ethanol, dropwise adding an ethanol solution containing chlorine into the device, and reacting at 14-16 ℃ for 0.2-1 hour after dropwise adding, wherein the molar ratio of the chlorine to the R-urea is 1.05;

and IV, dissolving NaOH in water to prepare an aqueous solution, slowly dripping the aqueous solution into the device, keeping the temperature of 4-6 ℃ for reaction for 0.5-1.5 hours, wherein the molar ratio of the NaOH to the R-based urea is 4.5-5.0, then filtering the reaction solution, and heating the filtrate to obtain a fraction at the temperature of 80-104 ℃ to obtain the special reducing agent R-based hydrazine.

4. The method for preparing the graphene additive for the heat-conducting silica gel material according to claim 3, wherein the specific reducing agent is prepared by a reaction process comprising:

5. the method as claimed in claim 1, wherein the graphene oxide solution is heated to 55 ℃ in S1.

6. The method for preparing the graphene additive for the heat-conducting silica gel material according to claim 1, wherein the volume ratio of the graphene oxide solution to the specific reducing agent in S2 is 1.

7. The method for preparing the graphene additive for the heat-conducting silica gel material according to claim 1, wherein the dropping speed of the specific reducing agent in the S2 is 0.1-0.12mL/S.

8. The method for preparing a graphene additive for a heat-conductive silicone material according to claim 1, wherein the temperature of vacuum drying in S3 is-11 to-9 ℃, and the drying time is 70 to 74 hours.

9. The method as claimed in claim 1, wherein the centrifugation speed of the centrifugation in S3 is 8000-10000r/min.