Modified recycled graphite as well as preparation method and application thereof
By heat treatment and silane coupling agent modification, the modified graphite is formed, which solves the problem of uneven dispersion of the recovered graphite in the resin and the low interfacial bonding strength, and significantly improves the mechanical properties of the resin composite material.
Patent Information
- Application Number
- CN202510236033.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-02-28
- Publication Date
- 2025-06-03
AI Technical Summary
When the graphite is recovered directly for resin modification in the prior art, there are problems such as uneven dispersion, low interfacial bonding strength, and small performance improvement range, making it difficult to effectively improve the mechanical properties of the resin composite material.
By heating the recovered graphite to 400-500°C and passing it into water vapor for heat treatment, the surface active groups and roughness are increased, and then the surface is modified with a silane coupling agent to form modified recovered graphite, which improves its dispersion and interface binding properties in the resin.
It significantly improves the mechanical properties of modified and recovered graphite-enhanced resin composite materials, the tensile strength and bending strength can be improved by more than 30%, and the elastic modulus and bending modulus can be improved by more than 100%. It is suitable for environments with high strength and high rigidity requirements.
Smart Images
Figure BDA0005292759610000071 
Figure BDA0005292759610000081
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of graphite modification, and particularly relates to a modified recycled graphite, a preparation method thereof, and an application thereof. Background Art
[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art already known to those of ordinary skill in the art.
[0003] Graphite is an important carbon material with excellent electrical conductivity, high-temperature resistance, and lubricity, and is widely used in fields such as batteries, lubricants, iron and steel smelting, and electrode materials. Graphite powder is usually obtained through mineral mining and processing. With the surging global demand for graphite, high-quality natural resources are gradually depleted, and the mining cost is also rising continuously. At the same time, the production process of graphite parts generates a large amount of waste, which burdens the environment, and these wastes contain graphite powder that has not been fully utilized. Therefore, it is particularly important to recycle existing resources, which can effectively reduce the emission of these wastes, thereby helping to reduce the carbon footprint and address climate change. At the same time, it can also significantly reduce production costs, enhance product competitiveness, and create new materials with high added value. However, there is currently little research on the modification and application of recycled graphite. When recycled graphite is directly used for resin modification, there are often problems such as uneven dispersion, low interfacial bonding strength, and limited improvement in performance. Therefore, it is necessary to invent a preparation method for modified recycled graphite to significantly improve the performance of reinforced resin composites and expand the application scenarios. Summary of the Invention
[0004] In view of this, the present invention provides a modified recycled graphite, a preparation method thereof, and an application thereof. The present invention modifies recycled graphite and uses it to reinforce resin, so that the finally obtained modified recycled graphite-reinforced resin has good mechanical properties and broad application prospects.
[0005] In a first aspect, the present invention provides a preparation method for modified recycled graphite, comprising the following steps:
[0006] S1. Heat the recycled graphite to 400-500°C, then introduce water vapor and perform heat treatment for 1-10 hours to obtain heat-treated recycled graphite;
[0007] S2. Fully hydrolyze the silane coupling agent in a solvent, then add the heat-treated recycled graphite, stir and react, then perform suction filtration, washing, and drying to obtain modified recycled graphite.
[0008] In a second aspect, the present invention provides the modified recycled graphite prepared by the above preparation method.
[0009] In a third aspect, the present invention provides a modified recycled graphite-reinforced resin composite material, which includes a resin and the above-mentioned modified recycled graphite, and the mass fraction of the modified recycled graphite in the modified recycled graphite-reinforced resin composite material is 15-25 wt%.
[0010] Compared with the prior art, the present invention has achieved the following beneficial effects:
[0011] The present invention uses inexpensive recycled graphite as a raw material, and prepares modified recycled graphite by a special modification method, which greatly increases its surface active groups and surface roughness. When it is applied to a reinforced resin composite material, the mechanical properties of the material are significantly improved. The tensile strength and flexural strength can be increased by more than 30%, and the elastic modulus and flexural modulus can be increased by more than 100%, making it have good application prospects in environments with high strength and high rigidity requirements. The preparation method of the present invention is simple, and it can also make full use of recycled graphite, with low cost, suitable for large-scale industrial application, and strong practicability. Specific embodiments
[0012] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.
[0013] The present invention provides a preparation method of modified recycled graphite, which includes the following steps:
[0014] S1. Heat the recycled graphite to 400-500 °C, then introduce water vapor and perform heat treatment for 1-10 h to obtain heat-treated recycled graphite;
[0015] S2. Hydrolyze the silane coupling agent sufficiently in a solvent, then add the heat-treated recycled graphite, stir and react, then perform suction filtration, washing, and drying to obtain the modified recycled graphite.
[0016] The recycled graphite mentioned in the present invention is graphite waste generated during the production of high-purity graphite parts (such as graphite electrodes, graphite crucibles, etc.), which has the advantage of low cost. Firstly, the present invention utilizes high-temperature heat treatment with water vapor. On the one hand, this step can promote the modification of oxygen-containing groups on the graphite surface. On the other hand, it can also play a certain cleaning role, enabling some impurities in the graphite to pyrolyze at high temperature. In addition, it can significantly increase the surface roughness of the recycled graphite, thereby improving the interfacial bonding performance during subsequent applications. The temperature of the high-temperature heat treatment will also affect the performance of the recycled graphite. Too high or too low temperature is not conducive to the introduction of oxygen-containing groups and the construction of appropriate surface roughness. Then, the present invention modifies the heat-treated recycled graphite with a silane coupling agent so that the silane coupling agent is grafted onto the surface of the recycled graphite, thereby introducing reactive groups and greatly increasing its surface activity. By combining physical and chemical effects, the two effects make the surface of the obtained modified recycled graphite have abundant reactive groups, can be fully dispersed in the resin matrix, and have good interfacial bonding performance with the resin matrix, thereby greatly increasing the mechanical properties of the resin matrix.
[0017] In the present invention, in step S1, the heating process and the heat treatment process are carried out in an inert atmosphere, and the inert atmosphere is selected from one or more of nitrogen or rare gases. The present invention does not impose special restrictions on the heating rate of the heating process, and preferably it is 2 - 10 °C / min. The heat treatment time is more preferably 2 - 5 h.
[0018] In the present invention, the water vapor contains an acid or a base with a concentration of 0.1 - 1 vol%. The addition of the acid or the base can further increase the surface roughness of the recycled graphite. However, it should be noted that when using an acid or a base, a quartz furnace body or a ceramic furnace body needs to be used to avoid corrosion. The preparation method of the water vapor containing an acid or a base is to first heat the aqueous solution containing an acid or a base to boiling to generate steam, and then introduce the steam into the reaction furnace body. The acid is selected from sulfuric acid, nitric acid or acetic acid, and the base is selected from sodium hydroxide or potassium hydroxide.
[0019] In the present invention, the silane coupling agent is KH570, which has good reactivity and good interfacial bonding performance with the resin matrix. The solvent is a mixed solvent of water and ethanol. The present invention does not impose special restrictions on the dosage ratio of the two, as long as KH570 can be fully dissolved in the solvent. Further, the step of fully hydrolyzing the silane coupling agent in the solvent is: adjusting the pH of the mixed solvent of water and ethanol to 3 - 4 with acetic acid, then adding the silane coupling agent, and stirring at 40 - 60 °C for 0.5 - 5 h.
[0020] In the present invention, the mass ratio of the silane coupling agent to the heat-treated recycled graphite is (0.5 - 1):100; the mass ratio of the silane coupling agent to the solvent is (0.5 - 1):(400 - 600).
[0021] In the present invention, in step S2, the temperature of the stirring reaction is 20 to 45 °C, more preferably 30 to 40 °C; the time of the stirring reaction is 0.5 to 5 h. The present invention does not impose special restrictions on the rotation speed of the stirring.
[0022] The present invention also provides modified recycled graphite prepared by the above preparation method.
[0023] The present invention also provides a modified recycled graphite reinforced resin composite, comprising a resin and the above-mentioned modified recycled graphite, and the mass fraction of the modified recycled graphite in the modified recycled graphite reinforced resin composite is 15 to 25 wt%.
[0024] The present invention does not impose special restrictions on the specific preparation method of the modified recycled graphite reinforced resin composite, and the preparation method of the reinforced resin composite commonly used in the art can be adopted. The present invention preferably kneads and extrudes the resin and the above-mentioned modified recycled graphite in a torque rheometer, and then performs hot pressing and forming through a flat vulcanizing machine to obtain the product.
[0025] In the present invention, the resin includes a thermosetting resin or a thermoplastic resin. The thermosetting resin includes unsaturated polyester resin, vinyl ester resin, epoxy resin, phenolic resin, etc., and the thermoplastic resin includes polyethylene, polypropylene, ABS resin, polycarbonate, polyacetal, polyamide, polystyrene, polyphenylene sulfide, etc. In one or more embodiments of the present invention, polypropylene resin is selected.
[0026] The technical solution of the present invention will be further described below in conjunction with specific embodiments. Unless otherwise specified, the present invention does not impose special restrictions on the sources of the reagents used in the following examples, and commercially available products well-known to those skilled in the art can be used. The recycled graphite used in the following examples of the present invention is graphite waste generated during the production of graphite electrodes.
[0027] Example 1
[0028] This example provides a preparation method of modified recycled graphite.
[0029] (1) Place 100 g of recycled graphite in a quartz tube furnace, evacuate and then introduce nitrogen, then heat it to 450 °C at a heating rate of 5 °C / min, then introduce water vapor to perform heat treatment on the recycled graphite, the water vapor treatment time is 3 h, and then cool it to room temperature with the furnace to obtain the heat-treated recycled graphite, and grind it for standby.
[0030] (2) Weigh 450 g of deionized water and 50 g of ethanol separately and mix them. Put them into a water bath at 50 °C and stir with a stirrer. Set the rotation speed to 460 r / min. Then slowly add acetic acid and adjust the pH value to 3 - 4. Then add 0.75 g of KH570 dropwise and stir for 1 h to fully hydrolyze KH570.
[0031] (3) Turn off the heating of the water bath. After the water temperature drops to 35 °C, slowly add 100 g of the heat-treated recycled graphite in step (1). Set the rotation speed to 600 r / min and continue to stir for 1 h.
[0032] (4) After stirring is completed, filter the graphite powder through a suction filtration device and wash it with ethanol.
[0033] (5) Dry it in a vacuum drying oven at a drying temperature of 70 °C until it reaches a constant weight, and then the modified recycled graphite is obtained.
[0034] Example 2
[0035] Compared with Example 1, the difference in this example is that the water vapor in step (1) contains 0.5% vol of sulfuric acid vapor.
[0036] Example 3
[0037] Compared with Example 1, the difference in this example is that the water vapor in step (1) contains 0.5% vol of sodium hydroxide vapor.
[0038] Comparative Example 1
[0039] Compared with Example 1, the difference in this comparative example is that step (1) is not carried out.
[0040] Comparative Example 2
[0041] Compared with Example 1, the difference in this comparative example is that steps (2) to (5) are not carried out.
[0042] Comparative Example 3
[0043] Compared with Example 1, the difference in this comparative example is that no water vapor is introduced in step (1).
[0044] Comparative Example 4
[0045] Compared with Example 1, the difference in this comparative example is that in step (1), the temperature is raised to 300 °C at a heating rate of 5 °C / min, and then water vapor is introduced to heat-treat the recycled graphite.
[0046] Comparative Example 5
[0047] This comparative example is different from Example 1 in that in step (1), the temperature is raised to 800 °C at a heating rate of 5 °C / min, and then water vapor is introduced to heat-treat the recycled graphite.
[0048] Comparative Example 6
[0049] This comparative example does not modify the recycled graphite.
[0050] Test Example
[0051] The modified recycled graphite of Examples 1 to 3, the modified recycled graphite of Comparative Examples 1 to 5, and the unmodified recycled graphite of Comparative Example 6 were used to prepare graphite-reinforced polypropylene resin composites. The specific preparation process is as follows:
[0052] (1) 200 g of polypropylene (PP) pellets were mixed evenly with 60 g of modified recycled graphite or unmodified recycled graphite; the temperature of each zone of the torque rheometer and the material temperature were set to 210 °C, the motor speed was 40 r / min, and the machine was preheated; the modified recycled graphite or unmodified recycled graphite and the pellets were poured into the torque rheometer, the motor was started, and the mixture was kneaded for 30 min. The material was extruded and cooled naturally to obtain a blend.
[0053] (2) 100 g of the above blend was weighed and preheated in a vacuum drying oven at a preheating temperature of 185 °C for 30 min. The preheated material was stacked in a mold of 250 × 20 × 2 mm. The temperatures of the upper and lower hot plates of the flat vulcanizer were set to 190 °C, and the pressure gauge was 10 MPa.
[0054] (3) The distance between the upper and lower hot plates was adjusted to make the mold contact the hot plates. After the temperature in the mold reached 190 °C, it was slowly pressed, and air was exhausted 5 times during the pressing process. After the upper plate of the mold was pressed flush with the mold frame, it was kept warm and pressurized for 6 min; then it was naturally cooled to 110 °C, and the mold was taken out of the vulcanizer to obtain a graphite-reinforced polypropylene resin composite sample plate.
[0055] The mechanical properties (including tensile strength, flexural strength, and Young's modulus) and thermal conductivity of the graphite-reinforced polypropylene resin composite sample plates prepared from different modified recycled graphite and unmodified recycled graphite were measured, and the results are summarized in Table 1.
[0056] Table 1 Performance test data of graphite-reinforced polypropylene resin composite sample plates
[0057]
[0058]
[0059] Note: * The polypropylene sample plate refers to the polypropylene sample plate without added recycled graphite.
[0060] As can be seen from Table 1, the mechanical properties of the graphite-reinforced polypropylene resin composite sample plates of Examples 1 to 3 of the present invention are significantly improved compared to the polypropylene sample plates. The tensile strength and flexural strength can be increased by more than 30%, and the elastic modulus and flexural modulus can be increased by more than 100%. The acids and alkalis contained in water vapor can further enhance the modification effect of recycled graphite. The measurements of Comparative Examples 1 to 6 show that whether steam heat treatment is carried out, the heat treatment temperature, and whether silane coupling agent modification is carried out will all affect the effect of recycled graphite. Although the mechanical properties thereof are improved compared to the polypropylene sample plates, the improvement amplitude is low.
[0061] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.
Claims
1. A method for preparing modified recycled graphite, characterized in that: The steps include: S1, heating the recovered graphite to 400-500° C., then introducing water vapor, and heat treating for 1-10 hours to obtain heat-treated recovered graphite; S2, fully hydrolyzing the silane coupling agent in a solvent, then adding the heat-treated recovered graphite, stirring to react, then filtering, washing, and drying to obtain the modified recovered graphite.
2. The preparation method according to claim 1, characterized in that In step S1, the temperature raising process and the heat treatment process are performed under an inert atmosphere, and the inert atmosphere is selected from one or more of nitrogen or rare gases.
3. The preparation method according to claim 1, characterized in that: The water vapor contains acid or alkali at a concentration of 0.1-1 vol%.
4. The preparation method according to claim 1, characterized in that: The silane coupling agent is KH570; and the solvent is a mixed solvent of water and ethanol.
5. The preparation method according to claim 4, characterized in that: The step of fully hydrolyzing the silane coupling agent in the solvent is: using acetic acid to adjust the pH of the mixed solvent of water and ethanol to 3-4, then adding the silane coupling agent, and stirring at 40-60° C. for 0.5-5 hours.
6. The preparation method according to claim 1, characterized in that: The mass ratio of the silane coupling agent to the heat-treated recycled graphite is (0.5-1):100; the mass ratio of the silane coupling agent to the solvent is (0.5-1):(400-600).
7. The preparation method according to claim 1, characterized in that: In step S2, the stirring reaction temperature is 20 to 45° C., and the stirring reaction time is 0.5 to 5 h.
8. The modified recycled graphite prepared by the preparation method according to any one of claims 1 to 7.
9. A modified recycled graphite reinforced resin composite material, characterized in that: The invention comprises resin and the modified recycled graphite as claimed in claim 8, wherein the mass fraction of the modified recycled graphite in the modified recycled graphite reinforced resin composite material is 15-25wt%.
10. The modified recycled graphite reinforced resin composite material according to claim 9, characterized in that: The resin includes a thermosetting resin or a thermoplastic resin.