Method for preparing graphene material by using waste masks

Abstract

This application provides a method for preparing graphene materials using waste masks. In this application, the PP layer material in the mask is infiltrated into silicone rubber, and with the assistance of the silicone cured on the PP layer material, the chain structure of the PP material is transformed into a ring structure during the laser processing of a laser engraving machine, thereby preparing a flexible graphene film. The graphene film prepared by the method of this application can not only play a certain role in alleviating the environmental pressure problem caused by waste masks, but also play a greater role by upgrading the material of waste masks to graphene to provide a flexible conductive material. The graphene obtained by the preparation of this application has excellent sensor performance and superhydrophobic characteristics, and experiments have proved that the graphene material provided by this application can be applied to the manufacture of temperature sensors, humidity sensors, and flexible sensors, which is of great significance for future application promotion.

Description

Technical Field

[0001] This application relates to the technical field of mask material recycling, and specifically relates to a method for preparing graphene materials from waste masks. Background Art

[0002] The current mainstream methods for recycling disposable waste masks have the following limitations:

[0003] 1. High-temperature incineration method: This method incinerates waste masks centrally at high temperatures, and the heat generated by combustion can be used for power generation. However, toxic substances are easily generated during the combustion process, polluting the environment.

[0004] 2. Landfill degradation method: This method uses microorganisms in the soil to complete the decomposition process, but the degradation time cycle is relatively long, and secondary pollution will be caused.

[0005] 3. Mechanical recycling method: This method crushes the masks and mixes them with other polymers for reuse. However, the product level produced by this method is lower than that of the original mask material.

[0006] 4. Chemical recycling method: This method converts masks into new materials through chemical processes. However, the current chemical recycling methods have complex processes and high energy consumption.

[0007] From the traditional recycling process of disposable masks, we can see that these methods all have certain limitations, and the performance of the recycled PP material often does not change, or a large amount of resources are required to improve its material performance for more utilization. Therefore, there is an urgent need for a technology that can upgrade PP materials at low cost to achieve more advanced applications. Summary of the Invention

[0008] In view of the deficiencies of the prior art, this application provides a method for preparing graphene materials from waste masks. With the assistance of solidified silicone, the PP layer material in the mask can be directly converted into graphene by laser processing, and graphene materials can be obtained at a relatively low cost to realize the resource recycling of waste masks. The specific technical solutions adopted in this application are as follows.

[0009] First, to achieve the above object, a method for preparing graphene materials from waste masks is proposed, and its steps include: First step, extract the PP layer material from disposable medical masks, immerse it in liquid silicone, and after the silicone soaks through the PP layer material, take out the PP layer material and lay it flat on the surface of the processing substrate; Second step, remove the excess silicone on the surface of the PP layer material and heat it to dryness to obtain the film to be processed; Third step, use a laser engraving machine to perform laser calcination processing on the surface of the film to be processed, and convert the PP layer material to obtain a graphene film with a preset pattern.

[0010] Optionally, in the first step of the method for preparing graphene materials from waste masks as described in any of the above, only one layer of PP layer material disposed in the middle of the mask is extracted, and after extrusion and leveling, it is immersed in liquid silicone with the melt-blown spinning side facing down.

[0011] Optionally, in the first step of the method for preparing graphene materials from waste masks as described in any of the above, the liquid silicone uniformly penetrates the melt-blown cloth layer of the disposable medical mask, and the liquid silicone can be cured after heating, and the silicone and the melt-blown cloth layer are integrated in the cured state.

[0012] Optionally, in the method for preparing graphene materials from waste masks as described in any of the above, the mixing ratio of glue A and glue B in the liquid silicone rubber is 1:1.

[0013] Optionally, in the second step of the method for preparing graphene materials from waste masks as described in any of the above, the heating and drying conditions are: a constant temperature heating table at 60°C to 80°C for 10 minutes.

[0014] Optionally, in the third step of the method for preparing graphene materials from waste masks as described in any of the above, during the processing of the laser engraving machine, its working current is set to 8.5 - 9.3 mA, the engraving speed is 20 - 80 mm / s, the logical resolution is between 400 - 1000 dpi, and the focal length is between 7 mm - 12 mm, and the graphene film with the best conductivity can be obtained. Through experimental determination, graphene films can be obtained when the working current is 8.5 - 9.3 mA, the engraving speed is 20 - 80 mm / s, the logical resolution is 400 - 1000 dpi, and the focal length is 7 mm - 12 mm.

[0015] Optionally, in the third step of the method for preparing graphene materials from waste masks as described in any of the above, the laser engraving machine is a CO2 infrared laser engraving machine. During the processing, its working current is set to 8.9 mA, the engraving speed is 30 mm / s, the logical resolution is 700 dpi, and the focal length is 9 mm.

[0016] Optionally, in the third step of the method for preparing graphene materials from waste masks as described in any of the above, the laser emission power of the CO2 infrared laser engraving machine is 3.6 W, or the laser processing temperature of the laser engraving machine is controlled at 3000 K.

[0017] Optionally, in the method for preparing graphene materials from waste masks as described in any of the above, the processing substrate is a clean glass sheet.

[0018] Optionally, in the first step of the method for preparing graphene materials using waste masks as described above, specifically, after leveling the middle PP melt-blown spinning material of a disposable medical mask to a thickness of 0.5 mm, it is laid flat on the surface of a processing substrate made of a clean glass sheet with the melt-blown spinning side facing downwards, and the PP melt-blown spinning material is soaked with liquid silicone so that the thickness reaches 1 mm after the PP melt-blown spinning material is mixed with the silicone. Beneficial effects

[0019] In this application, the PP layer material in the mask is infiltrated into silicone rubber, and with the assistance of the silicone cured on the PP layer material, the chain structure of the PP material is transformed into a cyclic structure during the laser processing of a laser engraving machine to prepare a flexible graphene film. The graphene film prepared by the method of this application can not only play a certain role in alleviating the environmental pressure problem caused by waste masks, but also can play a greater role by upgrading the materials of waste masks to graphene to provide flexible conductive materials. The graphene obtained by the preparation of this application has excellent sensor performance and superhydrophobic characteristics, and experiments have proved that the graphene material provided by this application can be applied to the manufacture of temperature sensors, humidity sensors, and flexible sensors, which is of great significance for future application promotion.

[0020] Other features and advantages of this application will be described in the subsequent specification, and part of them will become obvious from the specification or be understood by implementing this application. Description of the drawings

[0021] The drawings are used to provide a further understanding of this application, and constitute a part of the specification. Together with the embodiments of this application, they are used to explain this application and do not constitute a limitation to this application. In the drawings:

[0022] Figure 1 It is a sample diagram of the PP layer material in the mask infiltrated with silicone rubber in this application;

[0023] Figure 2 It is a sample diagram of the graphene film obtained after laser engraving of the thin film to be processed in this application;

[0024] Figure 3 It is a Raman diagram obtained by Raman testing the graphene film obtained in this application;

[0025] Figure 4 It is a microscopic structure image of the graphene film obtained in this application observed by scanning electron microscopy;

[0026] Figure 5 It is the comparison data of the hydrophobic angle sizes of the graphene film obtained in this application compared with the PP film, silicone rubber film, PP and silicone rubber hybrid film, and LIG film prepared by traditional processes;

[0027] Figure 6 It is the variation relationship between the resistance value of a temperature sensor prepared using the graphene film obtained in this application and the ambient temperature;

[0028] Figure 7 It is the variation relationship between the capacitance value of a humidity sensor prepared using the graphene film obtained in this application and the ambient humidity;

[0029] Figure 8 It is the variation relationship between the resistance value of a sensor prepared using the graphene film obtained in this application and the bending angle of the sensor. Specific embodiments

[0030] To make the objectives and technical solutions of the embodiments of this application clearer, the following will clearly and completely describe the technical solutions of the embodiments of this application with reference to the accompanying drawings of the embodiments of this application. Obviously, the described embodiments are some, but not all, of the embodiments of this application. All other embodiments obtained by those of ordinary skill in the art based on the described embodiments of this application without creative efforts shall fall within the scope of protection of this application.

[0031] Those skilled in the art of this technology can understand that, unless otherwise defined, all terms (including technical terms and scientific terms) used here have the same meaning as the general understanding of those of ordinary skill in the art in the field to which this application belongs. It should also be understood that terms such as those defined in a general dictionary should be understood to have a meaning consistent with the meaning in the context of the prior art, and will not be interpreted with an idealized or overly formal meaning unless defined as such here.

[0032] The meaning of "and / or" described in this application refers to the situation where each exists alone or both exist simultaneously.

[0033] Currently, in the process of preparing graphene by laser conversion, polyimide (PI) film is usually selected. It has a benzene ring structure and can be conveniently converted into graphene material by laser high-temperature processing.

[0034] PP material is usually used as the melt-blown cloth filter layer in masks. The molecular structure of PP material is chain-shaped and does not have a benzene ring structure. Therefore, graphene cannot be directly prepared by laser conversion. In existing research, phosphoric acid has been tried as a flame retardant. However, a large number of experiments have proved that phosphoric acid materials cannot play a flame retardant role for chain-shaped PP materials. Only carbon powder after combustion can be obtained after laser calcination and engraving, and graphene material with a two-dimensional honeycomb lattice structure cannot be obtained.

[0035] In view of the above technical dilemmas, the present application provides a method for preparing graphene materials from waste masks, which uses liquid silicone as an auxiliary medium to achieve the laser processing and engraving of PP materials to obtain graphene structures:

[0036] In the first step, the PP layer material in the mask is extracted and immersed in liquid silicone. After the silicone soaks through the PP layer material, the PP layer material is taken out and laid flat on the surface of the processing substrate in a Figure 1 manner.

[0037] In the second step, the excess silicone on the surface of the PP layer material is removed, and it is heated and dried to make the silicone material crosslinked and cured at high temperature between the PP film fibers, obtaining the film to be processed;

[0038] In the third step, the surface of the film to be processed is subjected to laser calcination processing with a laser engraving machine, and the graphene film with the Figure 2 preset pattern shown can be obtained by adjusting the laser power and the range of the laser scanning pattern.

[0039] The film material prepared by the above laser processing method was tested by Raman spectroscopy. By using a confocal micro-Raman spectrometer to perform Raman spectroscopy analysis on the generated graphene film, we obtained the Figure 2 2D peak that can determine that this material is graphene as shown. This proves that we processed a disposable medical mask infiltrated with liquid silicone by laser processing. By physically mixing the liquid silicone with the PP material intermediate layer of the disposable medical mask, and through appropriate laser processing power, speed, dpi, and focal length parameters, graphene was finally obtained on the disposable medical mask.

[0040] The present application overcomes the technical barrier that the PP material cannot form a graphene layer directly by carbonization under the traditional laser processing method. Obtaining graphene on disposable waste masks is a pioneering technology.

[0041] In addition, during the continuous testing of the performance of graphene materials prepared with different laser parameters in the present application, the above graphene preparation process was further optimized to obtain the following preparation technology:

[0042] 1. Pretreatment of the mask

[0043] The main component of the current disposable medical mask is polypropylene, i.e., PP. Generally, a disposable medical mask has three PP layers. To ensure the continuity of the PP layers, only the middle PP melt-blown spinning material of the mask can be taken and a relatively flat single-layer PP film material can be obtained by extruding and leveling it with a pressure of 80 g - 120 g. After extrusion, the melt-blown cloth structure of the mask will become denser. Therefore, immersing it in liquid silicone with the melt-blown spinning side facing down can make the PP fibers and silicone fuse more closely, and make the silicone evenly fuse between the PP melt-blown spinning fibers, so that a LIG with better electrical conductivity can be obtained after laser processing.

[0044] 2. Mixing of the mask and liquid silicone

[0045] Due to the process reasons of manufacturing masks, the two sides of the middle PP layer of the mask have different surface structures. Generally, one side is relatively flat, and the other side has the spinning produced by the melt-blown process. We can select the domestic Hongye brand silicone rubber as the liquid silicone for infiltrating the PP layer during the preparation process. Mix its A glue and B glue evenly according to the weight ratio of 1:1 and place them in a container with a relatively flat bottom such as a beaker. Then, immerse the PP layer of the mask with the spinning side facing down in the liquid silicone. After the silicone penetrates through the PP layer, take out the PP layer and place it on a clean glass slide with the spinning layer side facing up, and wipe the surface of the infiltrated PP layer clean with a tissue. The step of removing the residual silicone on the surface of the PP layer can prevent the residual silicone on the surface of the PP material from being directly laser-processed into SiC during the laser processing, which will affect the quality of the processed LIG. Place the processed PP layer mixed with liquid silicone on a constant-temperature heating table and keep it at a temperature between 60 - 80 °C for 10 minutes to heat and cure it, so that the melt-blown cloth layer of the disposable medical mask and the silicone are combined into one. Thus, the PP layer material crosslinked into a solid through high temperature, and after it is completely dried, the preliminary preparation work before laser processing is completed. The temperature of 60 - 80 °C is selected for drying and curing, mainly considering that: liquid silicone usually produces bubbles during the solidification process at a temperature exceeding 80 °C, and factors such as water vapor will affect the quality of LIG. When the set temperature is too low, such as below 60 °C, the solidification speed of silicone is too slow, which will also affect the quality of the processed LIG.

[0046] The PP film in the form of meltblown cloth used in this application can be fully and evenly mixed with silicone liquid. In the experiment, if common PP plates, PP cotton, PP filters and other materials on the market are directly used, even if the same silicone glue is coated on their surfaces, the silicone material can only remain on their surfaces and cannot be fully mixed with the above various types of PP materials evenly, and the physical bonding effect between the meltblown cloth PP film and the silicone glue in this application cannot be produced. Since silicone cannot be evenly mixed in the above PP material plates, PP cotton, PP filters and other materials, when laser engraving processing is carried out on the above PP materials of other textures, it will also fail to transform because it cannot be fully bonded with the glue. Using PP plates, PP cotton, or PP filters and other materials to replace the PP film recovered from masks in this application for laser transformation will only obtain carbon powder and cannot obtain graphene materials.

[0047] 3. Calibration of Laser Parameters

[0048] We selected the Keba Laser KB-4060 model laser engraving machine, controlled it through CorelDRAW software, and after multiple adjustments and tests, the best conductive graphene film can be obtained under the laser processing parameters of current 8.9 mA, speed 30 mm / s, logical resolution 700 dpi, and focal length 9 mm.

[0049] 4. Perform Raman spectroscopy tests on the film produced by the above laser processing steps.

[0050] By using a confocal micro-Raman spectrometer to perform Raman spectroscopy analysis on the produced graphene film, we obtained a 2D peak that can determine that this material is graphene. Therefore, we obtained graphene by laser processing a disposable medical mask mixed with silicone.

[0051] Observing it through an electron microscope will obtain Figure 4 the appearance structure shown. The hydrophobic angle data shown is measured through hydrophobicity-related experiments. From Figure 5 it can be seen that the graphene prepared in this application has a larger hydrophobic angle (L-PDMS) than the traditional process LIG material. The LIG film obtained in this application generally has a hydrophobic angle of more than 160 degrees, and its superhydrophobic properties can be widely applied to various fields such as antibacterial and the preparation of waterproof coatings. Figure 5 As can be seen from

[0052] 5. Perform temperature sensor, humidity sensor and flexible sensor tests on the laser-processed LIG. From Figure 6 、 Figure 7 and Figure 8 the various sensor tests shown, from Figure 6It can be seen from the schematic diagram that as the temperature increases, the resistance of the graphene material temperature sensor prepared in this application decreases linearly; from Figure 7 It can be seen from the schematic diagram that as the humidity increases, the capacitance of the graphene material humidity sensor prepared in this application increases exponentially; from Figure 8 It can be seen from the schematic diagram that as the bending angle changes, the resistance of the flexible sensor of the graphene material prepared in this application changes linearly within a certain range, and only mutates under extreme conditions close to 90-degree bending. All of these prove that the graphene prepared in this application has good stability and flexibility.

[0053] In other experiments, the flexible graphene film can also be prepared from the mask PP layer filter material in the following way in this application:

[0054] First, take the double-layer or triple-layer PP layer material in the mask, immerse it in silicone rubber. After the silicone rubber soaks through the PP layer material, take out the PP layer material and lay it flat on the surface of the processing substrate composed of clean glass slides;

[0055] Second step, remove the excess silicone rubber on the surface of the PP layer material, and place the infiltrated PP on a 60°C constant temperature heating table and keep it heated and cured for 10 minutes to obtain the film to be processed;

[0056] Third step, use a CO2 infrared laser engraving machine to perform laser conversion on the film to be processed. During the processing, through experimental determination, the PP film can be converted into graphene material under the working current of 8.5 - 9.3 mA, the engraving speed of 20 - 80 mm / s, the logical resolution of 400 - 1000 dpi, and the focal length of 7 mm - 12 mm. During the processing, the laser engraving machine can perform laser calcination processing on the surface of the film to be processed according to the preset pattern to obtain a graphene sensing film with specific electrical response capabilities.

[0057] During the above processing, it is preferably adopted Figure 1Prepare the PP melt-blown spunbonded film located in the middle layer of a disposable medical mask. During the preparation process, the thickness of the film is generally leveled to about 0.5 mm. The silicone rubber that infiltrates the pp layer of the mask is a hydrophobic silicone material. During this mixing process, the silicone rubber infiltrates into the voids in the middle layer of the waste mask and, to a certain extent, serves as a flame retardant to prevent the instant oxidation of the middle layer of the waste mask due to high temperature during laser processing. At the same time, the carbon atoms in the silicone rubber can serve as a carbon source to supplement the carbon atoms in the polypropylene in the mask film to form graphene. It has a better flame retardant effect compared to phosphoric acid selected in conventional methods, can effectively prevent the direct carbonization of the PP material by laser, and can also improve the conversion efficiency of the polypropylene film material in the mask into graphene material. Generally, a good flame retardant effect can be obtained and the PP conversion efficiency can be effectively improved when the silicone rubber and the PP melt-blown spunbonded film are mixed to a thickness of 1 mm. For the silicone rubber mixed PP melt-blown spunbonded film with a thickness of 1 mm, generally adjust the laser emission power of the CO2 infrared laser engraving machine to 3.6 W, or control the laser processing temperature of the laser engraving machine to 3000 K to obtain a better conversion effect.

[0058] The above is only the implementation mode of this application, and its description is relatively specific and detailed, but it should not be understood as a limitation to the patent scope of this application. It should be noted that for those of ordinary skill in the art, without departing from the concept of this application, several deformations and improvements can still be made, and these all belong to the protection scope of this application.

Claims

1. A method for preparing graphene materials from waste masks, characterized in that the steps are Including: The first step: Extract the PP layer material in the disposable medical mask, immerse it in liquid silicone, and after the liquid silicone soaks through the PP layer material, take out the PP layer material and lay it flat on the surface of the processing substrate; The second step: Remove the excess liquid silicone on the surface of the PP layer material and heat it for drying to obtain the film to be processed; The third step: Use a laser engraving machine to perform laser calcination processing on the surface of the film to be processed, and convert the PP layer material to obtain a graphene film with a preset pattern; Among them, the liquid silicone used to immerse the PP layer material during the preparation process is the domestic Hongye brand silicone rubber. Mix its A glue and B glue evenly according to the weight ratio of 1:1 and place them in a beaker. Then, place the side with the spunbond of the PP layer in the mask facing down and immerse it in the liquid silicone. After the liquid silicone penetrates through the PP layer, take out the PP layer and place it On a clean glass slide.

2. The method for preparing graphene materials by using waste masks according to claim 1, wherein In the first step, only extract one layer of PP layer material arranged in the middle of the mask, and after extruding and leveling it, immerse it in the liquid silicone with the meltblown spunbond side facing down.

3. The method for preparing graphene materials using waste masks according to claim 1, characterized in that, In the first step, the liquid silicone uniformly penetrates the meltblown cloth layer of the disposable medical mask, and the liquid silicone can be cured after heating. In the cured state, the liquid silicone is integrated with the meltblown cloth layer.

4. The method for preparing graphene materials using waste masks according to claim 1, characterized in that, The heating and drying conditions in the second step are: a constant temperature heating table at 60°C to 80°C for 10 minutes.

5. The method for preparing graphene materials by using waste masks according to claim 1, characterized in that, In the third step, during the processing of the laser engraving machine, set the working current of its laser head to 8.5-9.3 mA, the engraving speed to 20-80 mm / s, the logical resolution to be between 400-1000 dpi, and the focal length to be between 7 mm-12 mm.

6. The method for preparing graphene materials using waste masks according to claim 5, characterized in that, In the third step, the laser engraving machine is a CO2 infrared laser engraving machine. During the processing, set its working current to 8.9 mA, the engraving speed to 30 mm / s, the logical resolution to be 700 dpi, and the focal length to be 9 mm.

7. The method for preparing graphene materials using waste masks according to claim 6, wherein In the third step, the laser emission power of the CO2 infrared laser engraving machine is 3.6 W, or control the laser processing temperature of the laser engraving machine to be 3000 K.

8. The method for preparing graphene materials using waste masks as claimed in claim 1, wherein Among them, The processing substrate is a clean glass slide.

9. The method for preparing graphene materials by using waste masks according to claim 2, wherein Among them, In the first step, specifically level the middle layer of PP meltblown spunbond material in the disposable medical mask to a thickness of 0.5 mm, and then lay it flat on the surface of the processing substrate made of a clean glass slide with the meltblown spunbond side facing down. Soak the PP meltblown spunbond material with the liquid silicone so that the thickness reaches 1 mm after mixing the PP meltblown spunbond material and the liquid silicone.

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